Happy to answer as someone on the low key count side, simply put the benefit for me is comfort. Having a two key inner column reduces that awkward reach which is a pretty big improvement. I personally have pinkie pain so reducing pinkie keys completely down to just one key each lowers load and any reaches.

As noted you get rid of having dedicated keys as a side effect. By design those keys are low frequency or fit well with combos. Q and Z for example are super uncommon.

V is an almost a special case that works really well as a combo. V almost exclusively interacts with vowels, especially “e” and “i”. So with optimized layouts, it gets pushed to one of the worse positions on the consonant side. Usually top pinky or top inner.

The combo position is easier to reach and use over the pinkie or inner index. It is predictably preceded and followed by a vowel (or space), it is easy to keep a typing flow with the combo. (This V explanation is stolen and reworded from jcmkk3)

I’d say the same for / and quotes ring and middle move together and those combos are very comfortable compared to using your pinkies or at least my pinkies.