I imagine that’s the reason they let weapons drop in the vault…so that technically PvPers were still able to RNG a weapon like raiders can. Some PvPers as a community would have complained that PvE players could get a weapon straight away while PvPers were 100% time gated.
While I would have been open to weapons not dropping from the vault, getting lucky with RNG to get the right gear is a core aspect of the game and been around forever…gearing through PvE is all RNG that you not only get a drop, but also a piece with the right stats and one you don’t already have.