I think it's available in various wargames so that may explain the myth.
Part of the problem I see in that is they are pandering to the "What if?" crowd by creating those type of in-game prototypes, i.e. the never made ones. I get the Maus, or the E-50, or any of the others that at least were able to function as a tank during trials. You knew they at least worked, but maybe still weren't good enough. Designs that obviously weren't going to work, such as in this case do to issues of size constraint, don't accurately impact the game because the wow factor overrides the reality of how a vehicle with a gun that doesn't fit the turret is going to actually operate on the battlefield.
But, since the majority of folks in most any endeavor are of the group that cares to know more beyond the surface they will see such paper phonies in the listings and simply assume that because it is in there, it must have been a real or very possible vehicle. Newcomers to the genre see a few familiar tank types from movies and make the false connection that a few truths automatically makes all things true by association, even when no such promise has been made. Working in retail we used this to advantage by grouping less popular items around a very popular one to force impulse buying based on a false assumption that the others were as good as the popular one simply because we put them together. It is same thing as high school cliques. All based on erroneous assumption.
But, it is only a game run by a business and they are out to make money so if the people demand paper, then by gawd they will get paper and a plastic version to justify the $50 or whatever they spent on some pixels and bytes. It's not my business to run.