because for all the ways in which C sucks, it is the most common (lowest) denominator that ticks the portability checkbox.

This is actually something that Zig is supposed to do as well. There should be nothing that you can do in C but can't do in Zig. So hypothetically, in the future (say, twenty years from now), a Zig implementation of SQLite could be a preferred one since you're not losing anything with it. (With the additional benefit that should you want to, you might be able to compile application-specific queries into it.)