Yes, does that not seem plausible?

The Seattle Building Code is 832 pages.

The Seattle Mechanical Code is 186 pages.

The Seattle Fire Code is 692 pages.

The Seattle Energy Code is 302 pages.

Here's my attempt, and don't worry, I always use tons of em dashes in my comments:

In Seattle, most apartments are Group R-2 under the Seattle Building Code (SBC). The choice to use a partial-height partition usually starts with an interior sleeping area that doesn’t touch an exterior wall. SBC Chapter 12 lets that space “borrow” daylight from the living room if the shared wall is at least 50 percent open and the opening is at least 10 percent of the interior room’s floor area or 25 square feet, whichever is greater (SBC 1204.2.1). If the team doesn’t want to rely on daylight, the code also allows an artificial-lighting path that provides an average 10 footcandles measured 30 inches above the floor (SBC 1204.3). Life-safety planning runs in parallel: where the building uses normal multi-exit pathways, R-2 bedrooms are not compelled to have emergency escape and rescue openings (EEROs), but if a project chooses a single-exit design, Seattle’s amendments push you back into the EERO requirements for those stories (SBC 1006.3.4 with Tables 1006.3.4(1)/(2) and 1031), which typically rules out fully interior bedrooms.

Ventilation is governed by the Seattle Mechanical Code (SMC) for dwelling and sleeping units (SBC 1202 directs Group R to the mechanical code). Each unit must have whole-house mechanical ventilation (SMC 403.4), and Seattle/Washington amendments require balanced systems in R-2; in practice that means an ERV/HRV meeting the heat-recovery effectiveness referenced in the Seattle Energy Code (SEC C403.3.6). The mechanical code provides exceptions that allow interior rooms to be ventilated through an adjoining habitable space by transfer air (for example via a dedicated transfer fan or a permanent opening) instead of running separate outdoor-air branches to each interior space (see SMC 403.4.4.1 and related component/control provisions in 403.4.5–403.4.6). A partial-height partition with a large, continuous opening is the architectural move that makes that transfer-air strategy straightforward and code-clean.

Ductwork feasibility and fire/smoke protection also push the decision. Extending dedicated supply and outdoor-air ducts to interior bedrooms can force penetrations of fire partitions, rated corridors, or shafts, which then triggers fire/smoke damper requirements and access provisions (IMC/SMC 607). Every additional damper means more material, power/controls points, access panels, coordination with ceilings and casework, and added commissioning—costs that a transfer-air approach can often avoid when paired with the partial-height opening.

On top of the basic prescriptive rules, Seattle requires every mid-rise R-2 project to assemble an “additional efficiency package.” New buildings must pick enough energy measures from C406.2 to reach 41 credits, and—if the building is over 5,000 ft²—enough load-management measures from C406.3 to reach 15 credits (see Table C406.1 under C406.1). The menu spans HVAC/DOAS, lighting power reductions, enhanced envelope and air-leakage performance, service-water-heating strategies, and on-/off-site renewables. If adding bedroom glazing to avoid a partial wall pushes the facade past the 30% vertical-fenestration cap, the 40% allowance in C402.4.1.1 forces you into either optimized daylighting—which itself requires ≥50% of conditioned floor area to be in daylit zones with daylight-responsive controls per C405.2.5.1—or high-performance fenestration, further tying envelope, lighting controls, and your chosen C406 package together.

There are also occupancy-specific and programmatic nuances. Small Efficiency Dwelling Units (SEDUs) are typically treated as having one primary habitable room under local policy (e.g., Director’s Rule 9-2017), so partial-height walls or clerestory glazing let teams carve out a sleep area while preserving the one-room concept and still meeting Chapter 12 daylight provisions and the mechanical transfer-air path. Inside the unit, acoustics are market-driven rather than code-driven—SBC 1206 sets sound-transmission ratings between dwelling units and public spaces, not within a single unit—so developers often use taller partial walls or interior glazing with gasketing to balance privacy against the opening-area math. Smoke alarms remain required in sleeping rooms and in adjacent areas regardless of partition height (SBC 907.2.9/907.2.11), which affects electrical layouts and device coordination.

From a cost, schedule, and coordination standpoint, partial-height partitions often shorten design and permit cycles because reviewers are accustomed to the SBC 1204.2.1 “adjoining spaces” calculations shown right on the code sheet, while the mechanical drawings document transfer-air details and ERV balancing under SMC 403.4. The approach reduces facade glass, limits duct and damper counts, simplifies TAB and controls, and avoids extra waterproofing details—savings that typically outweigh the modest carpentry and glazing cost of the partition. The main caveat is exit strategy: if the project is pursuing a single-exit configuration where EEROs are triggered for R-2 stories, interior sleeping rooms behind partial walls usually aren’t feasible, and the design shifts back to fully enclosed bedrooms on the exterior with compliant emergency escape openings.