It must be taken into account that students can only say what they learned, but not what they didn't learn.
In YMVT, the pole and knives are too deeply related to the empty hand method and its training system to not have been part of its conception. Highly unlikely that YM created them himself long after the empty hand method had been developed.
I agree in that those likely were not added by YM, but certainly YM changes some items. We know he even changes items from his earliest Hong Kong students to his later ones, so it would seem reasonable to beleive he also changes other items before he arrived in HK. The swords are clearly Buddhist of origin based on historical records but who added them to WC is a mystery. The story is that the long pole came from the Junk Boat but again no proof. The more important thing is that we just do not know and the answer, if it exists, is somewhere in China awaiting discovery.