From what I’ve experienced through Apple, they don’t actually do a lot of ‘repairs’. They can definitely diagnose and replace components, but in terms of circuit level components, they just up and replace everything with a new part. They call these ‘Depot Repairs’. If you actually pay apple to fix liquid damage on your board, they will not even mess with any ultrasonic. They may not even have such machines in a Genius Bar (I can not verify that statement). So what you are asking doesn’t apply to Apple, so you have to use the thinking of, the indicator was already tripped when something was spilled. Your use of ultrasonic will mark that it was repaired properly.
If you browse the Mid-2012 Geekbench 4 results, you'll find that all of the highest scores have 2133MHz RAM inside of them. While this may likely just be coincidence that power users put in the best possible regardless of benefit, it does guarantee compatibility. Again, it stands that these systems can only address 1600MHz, and any faster will be slowed down (unless I am missing something). Might be a good experiment.