There is no such thing as optimization to take advantage of "the full capabilities" of these newer SSDs. We're talking about speed on a linear scale. Besides, SSDs have been in existence on multiplat games that also exist on PC for over a decade including NVMe half a decade. Third, the last gen games were already "optimized" for the newer consoles. It's plain the two consoles with always trade blows on load times. Sometimes the XSX's CPU will win the race, sometimes the PS5's SSD will. So far the XSX has won the majority of races.
XSX has VRS, along with a slew of other new DX12 features not on the PS5. PS5 has VRR.
Why the XSX isn't outperforming the PS5 on more titles out of the gate is a good question, but one also answered by the dev kit explanation. Neither the PS4 or XB1 introduced completely new API features, and Sony was similarly better known then for including simpler dev toolkits. It would perhaps be more appropriately analogized to the PS3 vs. X360 comparison where it was so difficult to develop for the Cell processor, which is why it lagged at the onset of that generation, but was producing a majority of titles known for generation-defining graphics by the end of their run. It won't take that long, in this case, since we aren't talking about a completely alien processor, but the analogy serves well.
It will outperform the PS5 with its large processing power advantage overhead. It's inevitable. I would advise skepticism of posters who insist otherwise. For example,
one is so ignorant of tech he read "VRR" to mean "virtual reality" just two weeks ago, but he'll posture as some sort of expert on these matters today. It's comical.