It seems like it would be good for non-March people, I'm not sure why the opposite is "obvious". For example if you're applying for an apartment and the other potential tenant is born in March, you'd an advantage even if you have a lower credit score- assuming we live in our current supply-constrained world, where housing is very zero-sum.
For a more extreme example, think of a situation where everyone born in March is sold into servitude, but only people born in February are allowed to own them. Is this good for people born in March? Obviously not. Is it good for people born in February? Absolutely, they'd be able to financially benefit from their newfound privilege. Is it good for people born in the other 10 months? Probably not, people born in March would skew the market for remaining jobs
For a more extreme example, think of a situation where everyone born in March is sold into servitude, but only people born in February are allowed to own them. Is this good for people born in March? Obviously not. Is it good for people born in February? Absolutely, they'd be able to financially benefit from their newfound privilege. Is it good for people born in the other 10 months? Probably not, people born in March would skew the market for remaining jobs