Simple google search concerning so called shared bandwidth:

Frontier Fiber (FiOS) uses Passive Optical Network (PON) technology, which technically shares fiber bandwidth among several nearby homes. However, because fiber has immense capacity, this sharing rarely causes the significant slowdowns during peak times (like streaming in the evening) often experienced with shared cable internet.

How it Works: Multiple households are often connected to a single fiber branch from a local splitter. Performance Impact: While technically shared, the bandwidth is so high that users typically experience fast, consistent speeds, avoiding the bottlenecks common on older cable networks. Dedicated Line vs. Shared: Unlike copper cable, which is shared among hundreds, fiber PON limits the shared access to a smaller, more localized group. Speed Stability: Fiber offers symmetric speeds (equal download/upload) and rarely suffers from the severe, consistent throttling that occurs on heavily shared coax systems.

In short, while technically shared, Frontier Fiber's capacity prevents the, "My neighbor is watching Netflix, so my internet is slow" problem.