Doesn't that put some film on your lens? I thought bounce sheets have "Static Guard" on them, which is a spray you can apply to things like seats and floors that are prone to static.
So the few particles of dust and lint that probably had no effect on output are replaced by a thin film of animal fats which is what anti static sheets use, and those definitely will negate any antireflective coating effects on that surface and reduce output transmission possibly by 4%.