TST: Make assert_extension_array_equal behavior consistent
- [X] closes #23709
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Doesn't seem like a whatsnew entry is needed for this, but can add one if need be.

This should also address #23605; I don't want to autoclose it, as I'd rather wait to confirm that the nightly build passes after this is merged.
