As far as I can tell, it is relatively rare for a legal name to also be the 'primary' alias for an artist in a certain locale. However it's not uncommon for users to check this combo, probably because 'legal name' seems super official - but that's now what 'primary' is meant to represent (see guidelines here)

We could add a little warning box, as we already do with non-title case in tracklists (MBS-13711), when this combo is checked. With text like:

"You have selected both 'primary' and 'legal name'. This combination is relatively uncommon: The artist's stage name, and translations of the stage name, is usually the primary name (the name that the artist performs as). Please double check before submitting. Click here for alias guidelines."