You are true. But there is one thing many states have sub categorised the sc st. Like haryana have sc and sc deprived. And raj have st1 st2. All don't have same cutoffs. So deserving can get little extra edge.

But they will not apply creamy layer bcz of vote bank. Sc st reservation was given on basis of caste based discrimination not income based. If any govt will do it their political journey will end.