Maybe a function of any lube or residual dirt still in the grooves?
When I pulled my carbs apart there was all sorts of hardened red "stuff" in the bowl Oring groove as well as the old Oring and silicone sealer (!). It was considerable work with a small hardwood "scraper," a toothbrush, and carb cleaner to get every trace of the gunk out. But once that was done, when I fitted the new Orings into the grooves, their own "stretch" held them in place.
FWIW, I did as suggested on this site - re used all the original Honda "brass." TBH I was a little concerned about the original float needles/seats sealing properly but once I finished the rebuild and bench synched the carbs, I installed them, turned on the fuel. No leaks and they function as new!