It wasn't ironic, at these "earlier" times it was common to use significantly stronger computers to develop for the "smaller targets": in 1975 Altair Basic, the first product of (then called) Micro-Soft, which had to run on the 8080 computer with only 4 kilobytes of memory was developed on the PDP-10 computer owned by Harvard University:
https://en.wikipedia.org/wiki/Altair_BASIC
Paul Allen wrote an emulator for the microprocessor which run on PDP-10. He was able to extend his previous version of emulator for that.
At the time Microsoft developed MS-DOS (actually modifying the program they have bought), around 1981, they owned their own DECSYSTEM-2060: