They are just doing their job to market their 2 SKUs as best as possible, one way to do that is to suggest they have no disadvantages compared to their competition, it's cut-throat business.
One thing I've been intrigued in their marketing of Series X is the use of term 'worlds most powerful' console instead of constantly throwing 12.1TF figure. They don't want to spend too much time dictating the metrics (like they did for Xbox One X) because there is a cheaper SKU to sell at launch too. Expect Lockhart to be pronounced as 'Worlds most economical' console or some shit like that lol
On their I/O solution, they are smart to have given a nomenclature for it. 'Xbox Velocity Architecture' has more buzz to it, compared to Sony doing a bunch of customization on die itself but not specifically naming it. Besides, the talk on I/O has picked up because MS are talking more about their API/Software, it can't make up for the hardware customization Sony have done on their end.
Team Green don't think Schreier is a legitimate source for consoles, he soiled his reputation to them when he chose to describe PS5 in few-choice words...
Warren is a MS lap-dog, he relays what his masters ask him to. If Lockhart wasn't launching parallelly and being revealed soon, I doubt he would've written that tweet out.
Any difference can be made noticeable if devs put work, even if said difference is 2TF. For 3rd-party stuff, if devs decide to use same resolution on PS5 and Series X (say 1800p), they can leverage that extra HP on Series X to make it more visually appealing. The question is if they would be willing to put the work in, or just play the resolution game like they did for PS4 Pro and Xbox One X.