The IBM PC was very much outside the IBM paradigm. On its mainframes IBM would do things like have chip manufacturers create custom part numbers or even rotate the integrated circuit inside the chip package to create non-standard pin locations to prevent other companies from upgrading or maintaining IBM computers. If IBM had done that, the IBM PC would have been an interesting note in computer history. Maybe Apple would have been the main computer people used and grown to be a big company.
Apple is bigger than IBM...........