https://drafts.csswg.org/css-sizing-3/#min-content-zero
Currently it says that semi-replaced elements e.g. <select> should respect the compressibility rules in both the block & inline directions.
Typically it is desirable to behave the same in both directions, but in this particular case it likely isn't desired.
The compressibility rules exist as the content size of size of these semi-replaced elements are fixed in a particular direction, e.g.
The inline-size of an <input type="text"> element is fixed, but the block-size isn't.
(Similarly field-sizing:content will disable the compressibility rule as well).
As such - these compressibility rules should only apply when the content-size is fixed in that dimension (and not if they aren't in the other dimension).