Perhaps there is some misunderstanding. TXHASH + CSFSV doesn't allow for complex or recursive covenants. Typically CAT is needed, at minimum, to create those sorts of things. TXHASH still amounts to deploying a non-recursive covenant construction.

This seems false to me.

<Only hash a single input scriptpubkey> txhash <only hash a single output scriptpubkey> txhash equalverify

Is that not a recursive covenant? With a little extra work you can also control for amounts and stuff.