Small frames are a pain in the arse for cyclocross as it makes it way more awkward to shoulder the bike without cracking your elbow on the chainring.
You're right when you talk about 50-ish cm frames, but certainly not with this kind of size.
My own "traditional" size is 58/60 cm c-t-t, but 57cm is not problem at all.
55cm is also fine, but 50cm (I also tried that for a whole season) is a bit problematic.
But: there are hardly any races, where you have to shoulder your bike, so what are we talking about?
You're right when you talk about 50-ish cm frames, but certainly not with this kind of size.
My own "traditional" size is 58/60 cm c-t-t, but 57cm is not problem at all.
55cm is also fine, but 50cm (I also tried that for a whole season) is a bit problematic.
But: there are hardly any races, where you have to shoulder your bike, so what are we talking about?