The explanation in the article is likely the right one.
These performance gaps, weird bugs, and differences between the Xbox Series X and PS5 versions of games look like issues related to the games rather than a platform problem for the Xbox. If Microsoft delivered dev kits and tools far later than Sony, then it could take creators more time to optimize further for Xbox. It may also explain why we didn’t see a lot of Xbox Series X gameplay in the months ahead of launch, but Sony was happy to regularly deliver PS5 gameplay.