Zed, I tested it again and the error is still reproduced. I’m using the Dutch WordPress (wordpress-5.8.1-nl_NL).
I did the export before and after as you requested and noticed a difference related to the problem.
The initial export shows: nirvana_fonttitle:”General Font”
After the Save changes it shows: nirvana_fonttitle:”Algemeen lettertype”
The same difference for many other font settings.