When I press S in the netrw window to edit the sorting sequence, and replace the value with just *, it does nothing.
If I press S again the old default value is shown.
Vinegar took over maintaining this option in #94 (discussion in #71). I hadn't considered that it would prevent manual override. @kiryph thoughts? Your proposed OptionSet solution is enticing. v:option_old can be used to derive if the sort sequence has been manually overridden, and if so, bail.