On the other hand, SSH gives you just that if you verify the fingerprint which is not mentioned in the guide. MITM-proof channel is needed if one gains any kind

On the other hand, SSH gives you just that if you verify the fingerprint which is not mentioned in the guide. MITM-proof channel is needed if one gains any kind of shell access because then public key substitution can happen in various ways, even without the user him/herself explicitly editing the file. Furthermore, if one allows MITM when accessing shell, substituting the public key is just one of very serious security problems.