ἅπαξ = hapax = once
Strong's defines the word to mean: once, once for all
You presume the KJV is the only rendering used by non-catholics.
how the faith was delivered "once for all" at the time Jude was written when perhaps five other books had not been written yet (John, 1 John, 2 John, 3 John, and Revelation).
I think the Holy Spirit knew what He was doing as the Scriptures were being revealed to the writers.