The purpose of block grants is to change an entitlement to a budget line item, which both stops it from expanding in a recession and also, in theory, lets the feds take a big whack at the total without having to deal with the consequences on an individual level because the states can decide who gets cuts.
States won't just recreate the federal policy because a) they'll be getting less money, which will bite when there's a real recession again, and also because b) we've seen with Medicaid expansion that several states in certain regions of the country will take the opportunity to end the program for most recipients ("they don't vote for us anyway") and use the money in some other way.
Yeah, and unduly Balkanized social safety net structures based on state lines are just horrible public policy. Folks start moving around more based on local transfer payment structures. Did I ever tell you that I am not enamored much with states' rights?
Sure let them be experimental laboratories from time to time where such toe dipping into the waters is a good idea, to test out what works or not, but that is a matter of prudence, not right.
One thing about Jeb that I don't like much, is that he is not a very imaginative man, or one who thinks out of the box much. He's more of a plodder.