[SolAndLuna]

It's really hard to take it as "intended" in either case. The description for the weapon only states powering up spells of the appropriate type, whether they use a weapon or not should only matter if the description states as much. Especially when there are other items where their effects work fine regardless of what is used, like The Kiss Farewell activating Auto Charge even if you defeat an enemy without using the gun, or even any weapon at all.

Ultimately, it's either a misleading description on a series of weapons that's hard to get, thus potentially wasting countless hours of someone's time and effort for nothing, or it's the weapon not properly adhering to its own description, which leads to the same issue. In either case, something should be done about it.