I'll take every opportunity I can to remind TF readers of this simple truism where cored composite is concerned, never rely on caulk, sealant, bedding etc to keep water out of cored structures. Caulk is a temporary affair, it dries out and fails, sometimes in a year, sometimes in 7 or 10 years, but in most deck cases it eventually will leak.
This article goes into some detail on the subject.
https://stevedmarineconsulting.com/c...deck-hardware/
(Attending the Marine Equipment Trade Show, Amsterdam, the Netherlands)