alt Hacker News> I would guess that using the tab key in this way was part of a patent they were pursuing and Microsoft's use would show this to be 'obvious' and thus not patentable.
IBM insisting it not to be tab wouldn’t make sense. Microsoft was working for them and the programs should adhere to the CUA (Common User Access) standard.
OS/2 1.0 and the first edition of the CUA were both released in December 1987 according to Wikipedia; Raymond's story isn't dated but could've happened before this. (If I had to make a wild guess, I could imagine this request was a side effect of some internal IBM battle about what the CUA should dictate).