Ask a kernel developer

Yeah, so they can lie to your face. No! They usually publish the higher thing their lawyers think they get away with publishing, with small letters saying "your load must be this that and thatotherthing and the hardware must support whatmacallit else those are invalid etc".

Seriously (and I developed an audio recording platform with some specific latency requirements), evaluate (hint: I ended up choosing a run-of-the-mill Linux kernel + glibc base).