Depending upon the game, some more significant than others with some being better using pcie Gen2 . Still overall with current Ryzen 3 generation a slight improvement. Once Ryzen 4 hits, this may change somewhat. There is more than just bandwidth at play, latency can also have an effect with pcie 4 being better. Was mentioned DirectStorage and RTX I/O, I would think both of those technologies may actually reduce latency and reduce load on the pcie bus, at least RTX I/O would making pcie 3 and 4 even less significant since the data is compressed and smaller in size. Unless games change dramatically faster in how content is streamed from the SSDs to the GPU, probably a couple generations down the line.
Ampere looks like a good upgrade from Pascal with some potential issues, power/heat being #1, Hardware Unbox as well as DF had some driver issues (probably be fixed).
I say the interesting flipflop has more to do with margins of error.
One of the review sites looked at the pcie4 feature test in 3dmark, and its exactly where it should be.
DirectStorage is going to eat bandwidth in the PCIe bus. Its just taking a hop out of the equation. Instead of certain data going to the CPU first, its going to go straight to the GPU. Throughput between GPU and nvme drive I believe is going to be way faster compared to throughput between nvme->cpu->gpu.
RTX I/O I believe is just a name that NVIDIA is using to advertise a feature set that includes DirectStorage as well as that AI noise reduction thing