The difference is providing a short succinct message that is either familiar or can be looked up as rg does here, vs vaguely saying invalid name without saying why.
It worsens the UX for no reason.
As a sibling comment said, the program already knows why the name was invalid. It would have cost nothing to surface the reason when reporting the error.
I'm not arguing that I think "Invalid name" is a good message here. I don't think it is. But if you're relying on either familiarity or the ability to look it up, then you're still relying on there being a manual to provide that information in the first place if it is not somehow included in the error message itself. As would be the case here with Bee and rg.
It worsens the UX for no reason.
As a sibling comment said, the program already knows why the name was invalid. It would have cost nothing to surface the reason when reporting the error.