Ours is the same way and I've been told numerous times that it is normal. If you listen and compare the speeds very closely, you should be able to tell that there is a very slight difference between the two settings.
I think there have been some threads on this in the iRV2 Winnebago owners' forum. I'll see if I can find any of them but if not, maybe you can post your inquiry over there.
Winnebago Industries Owner's Forum - iRV2 Forums
eta: I found one old thread on it but I'm sure there are others lurking in the archives. Somebody on this thread has reported only a 1-amp difference showing on the panel between speeds so as I say, it's a very slight difference. With ours, as I said, if I listen closely, I can detect a very slight difference: