Well for starters TB III is not truly water proof as indicated by the tests
it passes. IIRC the tests never mention water proof, only water resistant.

Dunno about the tests, but I have a bottle right in front of me, and it
says "Waterproof" TWICE right on the front label.
Haven't tested the waterproofness or even pushed the open time limits,
but I'm happy with it as a normal wood glue.
Andy