To prepare for or to use during?
During a race you want something that will absorb quickly and completely. Huel is rather low GI and has plenty of fiber, so it fails in both of those categories.
It might be something nice to have as a mid-race snack (to replace a bag of crisps or a candy bar or something) but I wouldn’t fuel with it.
I wouldn’t use it for a post-race recovery for stage races as you want something that’s gonna absorb as quickly as possible during the 2-ish hour window your body is most rapidly restoring your glycogen stores. After that 2-hour window I think it could work fine.