I really enjoy coding in C (it's probably the language I know the best) and I think C++ is an over-engineered and bloated language, however I'd still pick the latter for something like that. Or rather, like most devs, I'd pick a decently small subset of C++. The main reason for that is that in C if you need a data structure that's more involved that a simple contiguous array then you're on your own. A linked list is sort of not too bad to implement (the kernel's list.h is easy to use and reuse for instance) however as soon as you want things like hash tables, trees or anything that benefits from RAII IMO it becomes a pain to manage everything. It's perfectly possible to do all of that in C (or hell, in assembly if you want to) but in my experience it will take a lot of time to implement correctly (and since you don't have generics it's harder to have general purpose structures that you can reuse easily) and it'll have worse ergonomics because of a lack of destructors and other RAII patterns.

In my experience C is great for low level things (dealing with hardware, writing small low level services etc...). You don't have to deal with too many abstraction layers, memory management is generally straight forward (your average driver won't usually deal with anything more complex than a buffer queue or ring). For the type of application the author is talking about he'll probably have to deal with rather abstract data structure holding the state of the game, "a fluid flow of information coming into the app and going out of the app", concurrency issues etc...

Is it possible to do all that in C? Undoubtedly. If I was tasked to implement something like that would I choose C ? Hell now. I'd probably go with a subset of C++ like I mentioned before, Rust if the dependencies I needed were available (or I didn't mind coding them myself) or maybe even Python if I wanted to reduce development time as much as possible to get a PoC implementation live as fast as possible.