I did some work programming a sequence for a Siemens magnet, and while I can't comment on the quality of the code driving the hardware, the OOP API they exposed for sequence creation was as bad as it gets. There was no sense of abstraction at all; it was very much like someone took an old C-style library then systematically hid all the functions in different classes for fun. Now, I could imagine that someone somewhere declared the magnets would be cutting-edge C++, and that's exactly what happened.

The point is that OOP is not necessarily the obviously correct way to manage the complexity of an MRI sequence. Any other style could have easily been substituted and not done worse.