There are special mechanisms that permit certain DNAs to still function within the Barr Bodies. I'll share this article with you as a quick Google search: https://phys.org/news/2016-07-scientists-untangle-barr-body-inactive.html

Learned about how BBs are not silent while chatting with a professor in 2006. I suspect we don't know the exact details just yet, but could do a proper literature search. (Note: expertise is structural biology/biophysics. Almost went into epigenetics instead.)

Speaking in general about genetic expression and regulation, it's not just whether you have genes but also how many copies you have. Even though additional copies of X in a cell are packed away as Barr Bodies, this does not mean that they are completely silent.

So... people with XO end up with ovaries, but they are not functional for additional reasons.