"Jim" wrote
Polysulphide has a life span of 20 years. +/- How many of our boats are
that old?

I've never owned a boat newer than that.

My opinion here is that anyone who uses the term "goo" does not understand
the difference between the proper sealant for each job.

He may have meant Goop, which is a brand name sealer/adhesive that comes in
a marine version. I agree with your guess that there should be something on
the outside that that clamps that fitting to the fiberglass. Doesn't make
sense that it would just be held in with sealant, even good sealant.