It’s spending... authorized by Congress. 100% constitutional.
That said, we have a long history of having executive branch agencies writing the rules of implementation of such programs. I highly doubt original legislation was so detailed as to prevent HHS from making these kinds of low-level decisions.
“It’s spending... authorized by Congress. 100% constitutional.”
I would argue about it being Constitutional, but why? It’s spending and it’s being spent, Constitutional or not.