As noted in the jargon file, the dd(1) syntax is
deliberately reminiscent
of the DD statement in IBM JCL. This was presumably a joke
That is certainly true and reflects its major early usage to
prepare tapes to carry to other systems.
Though I haven't use dit in ages, I recall that the joke was
so fully engtained that the command was more likely to be
written "dd ifile=x ofile=y" than "dd <x >y"
Doug