How can I politely put this --- yes and no.
Some RG covers are equivalent to Storm's; some are very different. AS far as I know, they use the same chemical supplier, but the Sonic series has covers unique to RG. That's all I can say, at this point in time. Ask RG for mote intimate details.
Oh, the APocalypse, again, as far as I know, has a cover also unique to RG.
They DO design their own balls, not just cores, not just covers - they design the whole ball. Try one of them; you may like what you get.