What Is Confirmed
S-GAME presents enemy weapon acquisition as part of arsenal growth. The same listing promises more than 30 weapons and more than 20 Phantom Edges, although it does not say that every enemy weapon is obtainable or that all drops are random.
What Still Needs Testing
The retail build must confirm which foes award weapons, whether rewards are guaranteed, how difficulty affects acquisition, whether missed drops can be recovered, and how upgrades or duplicates work. Boss and weapon pages will link the exact source only after it is reproduced.
Source and Update Rule
This answer is based on the official Steam description. It will be updated if the retail build or an official announcement changes the wording.