MusicXML export cannot be re-imported cleanly

I have a very trivial example of a score that contains chord symbols. I've attached it below (example.mscz). If I export that file to MusicXML, I get what looks like a perfectly valid MusicXML file (which I can display perfectly successfully in the SoundSlice MusicXML viewer). However, when I re-import into MuseScore, the chord symbols are corrupted - they are not displayed correctly, and cannot be edited.

I've created screenshots of what SoundSlice and MuseScore render: https://imgur.com/a/aF9ISr1 - as you can see, MuseScore is rendering the score incorrectly. You should be able to get the same results by simply exporting the provided file as MusicXML.

I understand from other posts that MusicXML import has limitations, and that not all rendering details can be accurately reproduced. But this is not rendering, it's the basic structure of the score, and worse still, the file being imported is one that MuseScore exported itself!

Is this genuinely not supported usage? And if so, is there any supported input format that can be generated by an external program for import into MuseScore? Obviously, the above example of the issue is not my real use case - what I actually want to do is import scores that have been written in ABC notation. The existing plugins seem to all go via MusicXML, but as a result they fail to import chord charts correctly (or, for that matter, in any sort of usable form). If I can't import ABC notation or MusicXML files, I'll probably have to simply not use MuseScore, as having some form of text-based storage format for my scores is critical for me.