I think you're reading way too deep into marketing jargon. They called it the R5 to convey exactly where they expect to place it in the market. Why else would they jump right from EOS R to R5?
Also, the R5 does not have the vertical grip, large battery to go along with that, or the additional buttons on the front of the camera they reserve for their 1D level cameras. The R5 is meant as a 5D level camera, there's no question.
I agree partly, yes I still think they will come out with a 1D type full grip camera but this for me is NOT a 5D replacement, its entirely new.
If you look at the 5D line it has very incremental steps, this camera is leaps ahead of the current 5D. I have owned all the 5D line from the beginning.
Its going from,
7fps to 12/20fps
30mp to 45mp (rumored)
this is a huge jump and I'm all for it but its not a 5D replacement, its way above that in my opinion