At the beginning of a generation devs focus on the easiest to pullout performance. With Series X being sold out and being toe to toe with PS5 on sales at the start of the generation, your assertion sounds possible but not proven as a universal fact. It is a possible assumption
As a game company you cannot afford to do that and you generally will not do that. Especially with how expensive it is to make AAA games right now. Any potential savings for easier extraction of performance will be more than wiped out by any bad sales on the platform with the larger install base.
As such, when you go into a new generation budgeting for a new game will look to see first which platform will likely have the largest install base. That will be the one you're most likely to get the most return on money. Then you look to see what other platforms might be profitable to port to.
For this generation that meant PS5 as the PS4 had about a 2:1 install base lead over the Xbox. Any head of development who seriously considered Xbox as the lead platform either had some incredibly large cohones or they are a PC first developer with an easier dev. environment to move to Xbox or they were just inept or MS was paying them to make Xbox the lead platform.
There is
no financial reason to make Xbox the lead platform. And a very real potential for your title to make your company go bankrupt if you make Xbox the lead platform. As long as the PS5 version of your game runs as well as it can be made to run, you'll get most of your sales. If Xbox isn't polished or runs rough you lose a few sales but those are sales lost from a smaller install base anyway, so the impact is far less. If you instead have a badly optimized and rough PS5 version you stand to lose enough sales that your company may potentially go out of business.
In fact we saw that exact thing happen this generation in almost the worst way possible. Thankfully, it happened to a PC first company and sales of the PC version of their game was still enough to keep them afloat even though the fallout was so bad they had to ditch their in house engine for future titles and move to a 3rd party engine. That example? Cyberpunk 2077. If the PS version had been in the shape that the Xbox version was in they would not only have made a LOT more money but they likely would have been allowed to keep developing on their in house engine.
EA, UBIsoft, Square-Enix, SEGA (except their PC developers), Bandai Namco, ABK (pre acquisition), etc. all used the PS5 as the lead platform without fail. The only developers you'll find that might have done more work on Xbox than PlayStation would be the ones that still treat the PC as the lead platform (CDPR is the only AAA immediately coming to mind that is still PC first). 4A Games (Metro) and GSC Game World (Stalker) might still be PC first as well, although I'm not sure I'd classify GSC Game World as AAA. Hell, with the war in Ukraine if either were AAA before, they likely aren't AAA anymore.
Regards,
SB