I ran into this trying to do a Code theme a few months ago. (My favorite light theme -- and I am mostly a light theme person, as I have never believed dark mode was a particularly good idea except for terminal windows -- is the default theme from the all-but-defunct Mac editor Espresso, which used subtle background coloring in some places.)
https://github.com/Microsoft/vscode/issues/3429
I ran into this trying to do a Code theme a few months ago. (My favorite light theme -- and I am mostly a light theme person, as I have never believed dark mode was a particularly good idea except for terminal windows -- is the default theme from the all-but-defunct Mac editor Espresso, which used subtle background coloring in some places.)