In RL, railyards are not only important for train maintenance, but even more as hubs to organise freight and switch cars. Not enough of those and the rail systems gets clogged with traffic jams at the hubs, with trains waiting on side lines and a lot of freight still in the warehouses because freight cars could not get there to load it, so there is really a big consequence of this to the level of supplies available to the front troops.
For gameplay, you are probably right if the goal is to keep the Soviets resilient even after a very bad 1941/spring 1942. But I think we are touching on the old subject of where do we draw the line of Soviet resilience? Should the players abilities be leveled artificially to get most games to drag on beyond 1942 or not leveled to model RL and reward the best players? I was reading an old forum thread on this yesterday, they were discussing about the snowballing effect that would have using dynamic national morale levels determined by positions on the map instead of using fixed values going up or down with the years. Of course there were strong advocates for both point of views.
Railyards multipliers are IMO part of the same philosophic questions. Honestly, as a member of this WitE community I wouldn't be able to vote one way or another, because I can understand both point of views, after all we play WitE for fun, we are not students from a military academy, and I'm very much a team player from this point of view. But still, as a matter of personal preference, I would prefer WitE to be more simulation than game.
And I strongly suspect that in RL, if the Germans had captured Moscow and Leningrad, reached the Volga, and then captured Stalingrad, there would probably have been big political turmoils in USSR, which wouldn't have been very good for the health of the Red Army at all levels, resulting in the same kind of desintegration that happened to the Russian Imperial army in WWI.
"So much trouble in the world!" -Bob