Yep that's right, two main criteria, sheep carrying part has to be readily disinfect able and hose able, and it either has to have a ramp (with gates) or if no ramp the abbatoir/officials have to be happy that the sheep can be loaded and unloaded safely which means no jumping out. Hence some places are ok with lifting out small breeds or lambs, and some aren't, but none will be happy with large breeds who can't be lifted out.