Umm. It definitely didn't do a fallback. As you say, I think I just happened to have the fonts installed to render the math I was looking at. If I get the chance I'll have a look into it further tomorrow.
BTW: I've been fiddling around (the best way of putting it) with the accessibility matrix in Moodle Docs. I've made some changes. I wasn't sure what was required of the "Conversion to other formats" row, but I've added in information on how LaTeX and MathML are made accessible to the blind and visually impared. The conclusion is that basically you need a screen reader . I've no experience of OMML - I don't know if any screen reader supports it. Screen readers either use the DOM directly (depending on the browser), MSAA, or (more typically) a mixture of the two.
Hope this helps,
ASCIIMathML and MathPlayer
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