Text stretch does not work on default math font

[crack]

I have equations with lots of text in them, and the stretch text attribute is very useful for keeping them short.

In what seems to be a bug, line 1 does nothing, whereas line 2 does exactly what I need (but produces a pesky error and might not reliably work in later versions)

#show math.equation: set text(stretch: 50%)
#show math.equation: set text(font: "", stretch: 50%)

Is there a way to do this without the workaround?

[crack]

Upon closer inspection, the text is not being streched, but rather a more dense font is selected. This is desirable to me, but being able to select a font just for the text would also be nice. What is the name is the font it is falling back to?

$flag([the1, sr(fA, l1), the2, sco(l1, fB, J1, l2)]) = flag(the1)$
#show math.equation: set text(font: "")
$flag([the1, sr(fA, l1), the2, sco(l1, fB, J1, l2)]) = flag(the1)$