She did not know or care how humans were able to wield Noble Phantasms, but it appeared that they were not used to using them in actual combat. Even during this short battle, however, she could tell that their bodies were acclimatizing. The more they fought, the more power they would draw from their Noble Phantasms.
Even restricting her attention to nearby weapons, the power of their strikes and slashes was beginning to rise. Some had even begun to display traits unimaginable in ordinary weapons, such as a blade that emitted flames from its edge.
I can’t let them draw out this battle.

Fate/Strange Fake: Volume 2, Chapter 3 ("Day 1, Early Dawn")