Apparently the fact that the IBM PC came with MS-DOS was notable even in 1981:
Most surprisingly, IBM will initially be using outside sources of software and plans to accept programs from private individuals — a huge departure from past IBM practices.
New Personal Computers — now the big guns have arrived
IBM heads the list of new small-computer makersâ€” and that means big changes to come
By WILLIAM J. HAWKINS
The room was jammed. I was lucky to be up front; before me sat the demonstrator. His hands stretched across the keyboard as characters streamed onto the CRT display. It was a computer, a personal model for use in home or office. But it wasn’t just any new small computerâ€”this was an IBM.