That is not what the quote says. The quote says the PEP should not use performance as a motivation - independent of the PEP, performance improvements can of course be made where sensible.
I hope noone is argue for tuples because of thread saftey - this is just as incorrect of an assumption there as it is here. (For that you need something closer to PEP 795).
But again. The point is that the PEP shouldn’t exaggerate the guarantees - it may result in an incorrect perception by users that this data structure promises things it doesn’t and can’t.
Note that with maybe the exception of the last point, none of the things listed as requested by the SC are technical changes - they are all just requests to update docs to curb expectations.