Age Based Match Formulas

Can a plan have an age based match formula?  Assuming it would pass BRF testing.

For example:

50% of deferrals up to 6% of comp for those under age 45

75% of deferrals up to 6% of comp for those over age 45

Yes, I don't see why not if BRF satisfied.

Is there anything separate which would prevent the opposite layout being permitted, since age discrimination "only counts" when it's pro-youth?

ADEA?

That's what I figured - it might not be as "absolutely" easy as just passing BRF....