Looking at the current model year, the 22.5" 7.5 differs in at least 2 ways from the 20" 7.2 that may be relevant. (The same as between the 20" and 22.5" 7.2 FX)

The Head tube is 19 cm instead of 16 cm. If you have at least 3 cm of spacers to remove, this presents no problem. Based on my 20" 7.3, I think it would be close (I don't have the bike close by to check)

The other difference is that the trail listed changes from 7.0 to 6.2 I don't know how much difference this would make, but it is the only other relevant difference I noticed.