99% sure the autobrake applies regardless of whether or not you’re in free ride vs an event, at least that is what I gathered from @DavidP up thread:
“I’m not aware of any hidden logic that might cause this. There is also no distinction between events or free riding for physics (that I am sure).”
ETA: Good thread here from @Freighter on what sounds like the exact same thing I’m experiencing in any group setting (freeride, event, race, etc). Coasting on Zwift