What does that have to do with it? IBM didn't get that IRMA board from IBM either. It was necessary for IBM to have their PCs talking to their mainframes. IRMA was supplied by DCA, Inc., not made by IBM, and their boards were made for both PCs and Macs. I used to integrate different machines to connect to mainframes and terminals, much of it not being IBM. That included Wang, IVPhase, DEC and Apple (several models including Newtons). Back then it wasn't all IBM.
That point is that Apple wasn't going to lift a finger to get their computers to talk to an IBM mainframe. It fell to 3rd party vendors to make that happen. IBM didn't need to get cards from IRMA - they built their own, and would sell you a PC that would do it right out of the box.