Its a sort of epoxy... but not really glue epoxy, but more of a resin casting epoxy.
The reason for the tape, and release agent, is so it doesn't glue the neck to the body.
Imagine this - on metal to wood - we use car wax and release agent only. No tape. The entire barreled action (barrel and frame, minus trigger stuff) goes into the gunstock. It gets screwed down, the excess wiped off, and put away for a day. Then to get the metal out of the wood (hopefully), its one quick rap with the heel of your hand on the bottom of the barrel and usually it just comes out. Sometimes I had to back off the screws a turn, and give them a whack with a small hammer (and leather padding). Not stuck one in "for all time" yet, but.... I suppose it can happen.
Wood to wood fitting, I like to use tape, which allows for finish buildup and expansion of the woods. And it gives you that extra bit of security against gluing the damn thing solid. Usually wood to wood fit is meant to have a little play, unlike gluing the wood in solid, or, metal to wood, where you can get pretty near a zero gap fit.