"ROP attack methods are impacted because existing gadgets are transformed to consist of '<gadget artifacts> <mangle ret address> RET'. That pivots the return sequence off the ROP chain in a highly unpredictable and inconvenient fashion."
But you don't always have stack address leaks. Presently, in order to ROP you need (a) a leaked address to the space where your gadgets live and (b) the ability to write your ROP chain somewhere where the program will return into it. With this scheme, you now also need (c) the exact address where you are writing your ROP chain.
Not all info leak vulnerabilities leak arbitrary memory of the attacker's choosing. If they did, stack canaries would be pretty useless. So for those cases where a stack address leak is unavailable, this raises the bar against ROP.