So Pastebin and Github are more proof to you over an actual developer!?
Yes. They're hard data, they've come up around the time we'd expect, and they're numbers we can reliably trace and reference. And tbf, those aren't the only two sources; multiple GPU benchmarks have been datamined, those in reference to PS5 mainly still consistently being Oberon.
I could say I'm a developer too, but that wouldn't actually make me a developer (just as an example; I would hope the guy is being legit in their claim as a developer but it's not hard to fake that). And while I think the guy is probably affiliated with a development house in some way, there's no say to who that dev is, or his position in the hierarchy at that company.
Data & Statistics (and patterns in data and circumstantial results) > Blind Faith and Hearsay. Every. Single. Time.
But surely if the underlying tech is very powerful then it would be able to show itself on more powerful console (X) and make the game look better than what's on Playstation. No reason why they couldn't make a game like Uncharted on base Xbox and then upscale it to look superb on X. The reality is Sony devs are just much more talented.
Sony's got some of the best graphics artists in the biz, but they only got a chance to flex those skills because Sony gave them the budgets to do so. We know MS has suppressed most of their devs, particularly studios like Rare, from really flexing their potential.
When they let them flex themselves and give them some breathing room and budget, you get stuff like Hellblade 2 and Project:Mara. And yes those were in-engine but so was Uncharted 4's reveal trailer, and the final game pretty damn close to that reveal trailer.