I don't think xBA is a good stat. Aaron Judge is having a historically good season and his xBA is only .309. If you have to have a historic season to have an xBA over .300, then it's obviously underestimating a lot of hitters ability to hit for average.
For example, Jose Ramirez is beating his xBA by 20 pts.
I think you're misusing xBA. It's not to be taken literally, but is rather a tool to measure quality of contact