Yes, precisely -- you cannot use MT as as a CSPRNG; however, you can use a secure hash function as a CSPRNG, with MT as the sequence generator. But, you can use a secure hash function as a CSPRNG with just about any sequence of numbers, as long as no one knows what the seed is -- you just run it in output feedback mode.

Unfortunately, no one has done any kind of serious verification with MT + secure hash that I've been able to find; at least not to the extent of CSPRNG algorithms like ISAAC.