I agree. I think this is denoting a form of ignorance in that they are trying to let you know that their machine doesn’t NEED a neutral. The fact that the neutral exists at the source transformer is irrelevant. They just misinterpreted that as being the same as “delta”. The proper way to put that is “3 phase 3 wire + ground”, no need to reference if that is derived from a delta or wye source.
This is how 99% of MCCs are denoted, because motors (almost **) never need a neutral.
** I added “almost” because if I said “never”, someone would prove me wrong with some bizarre exception…