No, it's not. At 0.71x magnification 100% coverage viewfinder will be bigger than 97% coverage viewfinder. 6D and 5D3 both has 0.71x magnification viewfinders. APS-C cameras have smaller magnification, 7D, for example, has 0.63x, 50D has 0.59x.
The specs I read (Canon's own 7D brochure) say the 7D viewfinder is 1x magnification and 100% coverage.
Or do you mean that the 7D viewfinder is only 0.63x the size of the 5D/6D?
Yes, the 7D's magnification is either 1 or very close to it. You can put a 50mm lens on it and things look pretty much exactly the same size as they do through your other eye; in fact you can still have proper binocular vision with 1 eye looking through the finder and the other not.
That is definitely not the case with the 5D; its magnification is far lower.
As I say, my film camera does have 1x magnification, and is still (obviously) full-frame, so its viewfinder size is enormous compared to that of the 5D.
Canon 5D3 , 70-200mm f/2.8 L IS II , 24-105mm f/4 L IS , 50mm f/1.4 , 85mm f/1.8 , EF 2x III
Canon EOS M5 , EF-M 18-150 , Samyang EF-M 50mm T/1.3
Olympus OM2-SP , 50mm f/1.2 , 55mm f/1.2 , 50mm f/1.4 Silvernose , 135mm f/2.8 , 28mm f/2.