PVF is executed by a polkadot validator during backing, approvals and disputes. It's possible requests from those systems come in simultaneously. I don't know how many of those requests may come in concurrently, but it depends on the configuration. If I were to guess, then I would suppose there would be at most 3-4 PVF executing at the same time. Assuming those numbers, in the pathological case those PVF manage to fill the whole available memory at approx. the same time, it would make at most 512 MiB of committed memory with the current 128 MiB limit. With the new parameters the amount of memory consumed only by PVFs jumps up to 2 GiB.
So that makes me wonder if there were any testing done for what would happen with those pathological values on the standard hardware?