I've observed pretty much the same effects while using Dektol, Seletol, and 130. When I say "not change tone much" I'm talking the classic warmtone paper response to Se toner.
It's not just me either, MGIV has been widely reported as others as not toning "well" in selenium toner. Sure, it may go dmax faster, but as far as conversion of silver to silver selenide such that reflected light gives it a different color/tint entirely - MGIV is not that paper. Even if MCC takes longer, for whatever reason, the eventual end-result is more color shift. Selenium toning doesn't always have to be cold magenta. My go-to neutralish paper (when it was around) was Emaks #2/#3 and this always had a nice balanced tone in KRST and did not give off the feeling of "coldness." MCC also settles into a similar balanced look, I've found. MGIV, while a great paper, is like frozen grape juice in selenium.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.