You're right - their Technical Bulletin says one coat and their Product Data Sheet says three minimum. Also says don't let anything dry before the next coat until you've got the High Build Epoxy primer on (first coat, I'd assume.)
Their words suggest the Rustloc is the water proof part, so a specific barrier coat seems redundant, plus there is no fiberglass to protect from osmosis.
Good luck with it.
Craig - SN68 Sangaris, Tropic Isle Harbor, FL