The numbers are not for through latency (-> audio interface -> cpu -> audio interface ->)
Instead they are for "half-duplex" latency (-> audio interface -> cpu OR cpu -> audio interface ->).
The 48kHz number represents a buffer size of 32 samples, which is entirely possible with Linux and macOS. The note also does not indicate how h/w specific these numbers are: there can be many h/w level issues with very low latency numbers that can't be solved by the OS (a classic example is a wifi chipset or video interface hogging the PCI bus for too long). On the "right" h/w, 32 samples for input latency is not really that remarkable.
What would be remarkable is if MenuetOS can get this performance from arbitrary intel hardware.