In a fresh new project, collecting works as expected. However, once you go to collect a comp containing some asset(s), it seems to remember them moving forward and will start to ignore the For Selected Comps setting, even if you go back to selecting the empty comp(s). I've attached a very quick demo showcasing what I'm describing. I don't show it in this video, but I did test collecting the empty comp and it does indeed adhere to the footage listed at the end of the video. Opening that collected file shows all comps.
I've seen the "reduce project first, then collect" workaround recommended in the past, and that would work. Another workaround seems to be to close and reopen the project. That seems to make AE forget that you almost collected different comps before and it starts working as expected.
Overall it seems like a pretty finicky bug that can be tough to expose consistently.
Tested on:
AE Version 24.6.1 (another user confirmed on previous version and different OS)
Hardware Specs
3.8 GHz 8-Core Intel Core i7
AMD Radeon Pro 5500 XT 8 GB
32 GB 2667 MHz DDR4
MacOS 14.6.1