Of course not. Merging the basic infra for Rust didn't come with "it can be used in every single part of the kernel, regardless of what the people maintaining that think"-kind of guarantee. One way to use Rust is to only use it in drivers for example, and it seems Hellwig is not against that: "do that in your driver so that you have to do it".
Duplicating this wrapper in every driver would just make painful the usage of DMA for Rust drivers for not benefit.
I can see where he's coming from. I can also see why doing that is painful.
I don't really know what the best possible solution is. I do know that "Linus decided on Rust4Linux, therefore, this must be merged" is not a good argument. "Linus decided «moduke» is merged, therefore, accept my patches that are useful to «module» on «some other subsystem»". That doesn't really work, obviously.