Magic Mouse low charge indicator not working

I posted about this last year without getting any resolution, and I don't want to file it as a bug report yet, but why? It's a rechargeable one, not a battery-powered one, but still...

I can't upload images on this forum, but it's set to notify me when it drops below 20%. Nothing happens until macOS' notification that it's down to 2%, which of course is ridiculous.

TIA