Denoise changes exif data

I just noticed that for some weird reason, Denoise (and it may happen with other topaz products as well, not sure) changes the f-stop exif data. If the f-stop used was, say, f5.6


it changes it to


… which is close but it screws up my f-stop display in one of my apps:


Why is Topaz messing with my exif data?