The EE needs to be reminded that he's not an electrician, and that the NEC is not in the college curriculum.
For nearly any circuit (power cords to double-insulated tools being the only exception I can think of), we need a ground or fault path. Things still need to be bonded together.
For a branch circuit, the conduit can be the fault path. For a feeder or service, you need a wire.
Otherwise, you have the possibility of one piece of equipment becoming energized by 'phase A' and another being energized by 'phase B." Without bonding, this double fault will exist untol the two pieces are connected - maybe by you. Who want's to be nicnamed "Fuseboy?"
BTW, you have an 'ungrounded Delta.' An 'open Delta' is a three-phase system with only two transformers. Yes, it is possible to have an ungrounded, open Delta system.
