So when the OLF many years ago had a highly respected builder tell us they used epoxy for the fretboard I tried it as well. Must have done maybe ten that way and I used West Systems and System III. I preferred West only because it's a Michigan product and so am I
Then along comes my friend who is a master woodworker who even had his own woodworking TV show on the West Coast. He was here learning to build guitars and was a quick study.
My friend made the argument that epoxy is a bit like paint in so much as it never really, really fully cures and as such is a poor transmitter of vibration of all frequencies.
He went on to make the case that for HHG if you can't have clamps in place in the short open time there is no value that counters the risk of HHG's pitfalls meaning short open time. But he thought that Titebond Original was a good choice for fretboards.
I thought he made a great argument and I returned to using Titebond Original and I have to tell you it's much easier to use too than epoxy with clean-up being potentially a mess with epoxy.
The problem that epoxy was originally suggested to cure, pardon the pun was that water based glue when gluing on a fretboard can induce a bow of sorts in the neck. I had already been countering this by how I glued things with pressure in one direction from a stick going from the floor to the headstock with the neck clamped to a bench. The method works well, it's not mine, I read it somewhere. It also used to be described in the instructions for the Stew Mac Dread kit.
Anyway long story short the guys here citing the serviceability differences between epoxy and Titebond Original are spot on too. Much easier to get Titebond Original to release than epoxy when the mess comes alive again.