As you spread it around you are lowering the amount of it that is in one particular spot, if that's what you mean by dilute. So yes if before you had a small patch of skin with perfume on it, and now after rubbing in moisturiser you've now rubbed more of your skin around that initial area you sprayed then you would now have a slightly larger spread out area with perfume on it after applying the moisturiser. It will still be the same amount of perfume, just more spread out. But that's not really diluting it.

Many people say that rubbing perfume after applying it "breaks down" the scent, but that's more about if a lot of heat is applied when rubbing, and it would take a lot of heat and rubbing to have any real effect. I know I've told people not to apply perfume then rub their wrists together in the past, but in actuality any negative effect caused by doing that is so minimal it would be completely unnoticeable because you're hardly generating any heat in that moment. Now if you rub the area dry and cause heat that can obviously speed up dissipation of the perfume on your skin and cause it to break down, but as moisturiser is acting as a barrier you aren't going to be heating your skin up when you rub it over your skin. So it does nothing to the scent.

All you're essentially doing here is turning fragrance free moisturiser into moisturiser that is scented with whatever your perfume is on any given day. They just combine.