Rust's borrowing rules might force you to make different architecture choices than you would with C. But that's not what I was thinking about.
For a given rust function, where you might expect a C programmer to need to interact due to a change in the the C code, most of the lifetime rules will have already been hammered out before the needed updates to the rust code. It's possible, but unlikely, that the C programmer is going to need to significantly change what is being allocated and how.
If they completely replace an API then sure, probably.
But for most changes, like adding a param to a function or a struct, they basically have to learn nothing.
Rust isn't unlike C either. You can write a lot of it in a pretty C like fashion.