that is interesting. sounds like some of the bugs the Garmin has are not in the trek. but it has way too long and wide. Garmin is really bad about the wide going off while on bike paths and such the trek would be worse. and the stance back is plenty on the Garmin . sometimes too far.I found this comparison between Trek CarBack and the Garmin Varia RCT715. I am looking at these but not ready to take the plunge.
https://cyclingmagazine.ca/sections/gear-reviews/new-trek-carback-radar-vs-garmin-varia/