Its a little of column A, little of column B type situation.
Yes, some of it is his taste, but that taste is coming from a technical place. Primarily long term maintainability of the project.
I realize what Linus came out and said outlines that no code is entering Christoph's part of the project, but Christoph is playing goalie and needs to make sure that never happens in order to keep everything working correctly for a very long time.
Maybe the DMA module gets rewritten completely in Rust one day, but until then, rust modules interfacing with a C-only component seems to be the best for long-term maintenance.
It appears so now, yes, but when the drama initially came out it sounded like they were asking for a tiny amount of rust in the kernel to make it work, or if not rust, changing the C to tailor it specifically to the rust. Which I think is a reasonable thing to be concerned about from a maintainability perspective long-term, especially if the rust developers decide to leave randomly (Hector's abrupt quitting over this very issue is a prime example).