(not the parent) You're not wrong but you're not right either. There's basically a colloquialism where many developers say "runtime" to mean "large runtime" and "no runtime" to mean "small runtime," but that doesn't mean that crt0, the "c runtime starting from zero", doesn't exist, just that we've ended up in a place where this gets confusing to talk about because nobody uses the same definitions.
So if it's idiosyncratic really depends on what audience you're talking to.
It's the correct definition and I don't know of anyone familiar with OS design that would claim C doesn't have a runtime. It very much does. So does C++. Every language does, except assembly.
It may feel like C doesn't have a runtime if you're only familiar with UNIX, because the C runtime is guaranteed to come with the OS there whereas other language runtimes are optional and thus more visible. But every language has a runtime.
So if it's idiosyncratic really depends on what audience you're talking to.