What Bob said, also, some papers do exhibit a change while fixing, if you watch closely. I have used some which "cleared" noticeably in the past (an Eastern Euro paper, don't remember the brand, was the most obvious), and I could see somewhat a change as my old favorite, Forte MG Fiber cleared in TF4. Ilford MG doesn't show a change, that I can see under red lights.
I haven't compared closely, but I think the Ilford MG does look slightly cleaner, though, under white viewing light, if soaked in water for a minute or so after fixer, rather than taken straight from the fixer to viewing, as if final remains are cleared out by the water.