Paul Tomblin wrote:

That would only make sense if you had some evidence that the Soviets were
averse to propellor planes during that period. But their front-line
strategic bomber was a turboprop, and so were some of their airliners.

You're right, of course. I guess we'll have to find the designers and ask
them ;-)

My gut feeling is that it's an elaborate practical joke by the designers to
see how far they would get in the system.