It’s not that they don’t work, it’s that they’re not really single line.
TrueType and OpenType fonts are supposed to be closed, and won’t validate if open, so instead, what is done is very narrow glyphs are drawn, which causes the tool to double back.
“Real” single line fonts are available in specialty tools such as the “Hershey” fonts for which there is a plug-in for Inkscape:
https://www.evilmadscientist.com/2011/hershey-text-an-inkscape-extension-for-engraving-fonts/
(unfortunately, that site isn’t working at the moment — if need be, use the Wayback Machine link: Hershey Text: An Inkscape extension for engraving fonts | Evil Mad Scientist Laboratories )
A work-around is to use a suitably sized tool and inset an amount which the font design requires (note that this creates the same sort of distorted vector appearance as the fonts sold as “single line”)