Is it a good thing to have merges that never fail? Often a merge failure indicates a semantic conflict, not just "two changes in the same place". You want to be aware of and forced to manually deal with such cases.

I assume the proposed system addresses it somehow but I don't see it in my quick read of this.

They address this; it's not that they don't fail, in practice...

the key insight is that changes should be flagged as conflicting when they touch each other, giving you informative conflict presentation on top of a system which never actually fails.