I realize this is very late but as I didn't know there was any 40s compat before seeing the actual sales page I wanted to bring this up.
The 1.5 enter is pretty much exclusively used with the R2 1.75 backspace which is very unfortunately missing. For fewest keys maximum impact when it comes to 40s the recommendation is R2 1.75 backspace, R3 1.5 enter, R3 1.25 tab. 1.75 enter is usually excluded as it can be physically replaced with 1.75 control/caps lock.
It would do the 40s compat a world of good if the 1.75 enter could be replaced with a 1.75 backspace.