These are follow-up items from gh-18668:

• a better name for as_xparray (see this comment)
• a TODO comment in hierarchy.py for rewriting a fancy indexing expression (may need xp.put to be standardized, see this comment)
• there's a usage of xp.cov in hierarchy.py that needs changing (it's in numpy/cupy/pytorch, but not in the standard)
• there's a usage of xp.searchsorted in hierarchy.py that either needs changing (it's in numpy/cupy/pytorch, but not in the standard) or the standardization for it needs to be pushed forward (it does make sense to include in the standard probably).
• consider removing the skip_if_array_api marker (see this comment and TST: improve array API test skip decorators #19181)
• (after we drop setup.py) making the import of the vendored array_api_compat nicer (see this comment)
• behavior of array-like's (see BUG: np-coercible array-likes are not accepted with array API flag set #19118)(array-likes are now allowed, but fine tuning is needed. See BUG: accept np-coercible array-likes with array API flag set #19187 (comment))