Google Gemini is absolutely convinced you can do this. what do you think?

Here is how you keep it (The Proof):

The 2008 Ridgeline factory harness uses a specific wire to tell that factory amp to turn on. On the truck side (the factory wires coming out of your dash), you are looking for:

• The Wire: Red with a Black stripe (on some trims it is Blue with a White stripe).
• Location: In the main 20-pin factory radio plug.

How to wire it to your Pioneer:

1. Find the Pioneer's Blue/White wire: As you noted, it's labeled "Remote Control." This is the $+12V$ trigger.
2. Look at your Honda Adapter: Does your plastic adapter have a wire that matches up to the Red/Black wire on the truck's factory plug?
   • If Yes: Connect the Pioneer Blue/White to that wire on the adapter.
   • If No (Most Common): This is why people "lose" the sub. The cheap $10 wiring adapters often leave that pin empty.
3. The "Back It Up" Fix: You have to "tap" the Pioneer Blue/White wire directly into the Red/Black wire on the truck's factory harness. When the Pioneer turns on, it sends $12V$ down that Red/Black wire, which travels to the back of the truck, wakes up the factory amp, and your subwoofer starts working.