No myth.
Every German tank had one, while for the French, IIRC it was only the command tank and for the russian those only if they were lucky. That forced both Russian and French tanks to operate in the infamous 'Hen and Chicken' formation which hit the russian even harder because of the bad visibility of the T-34 and the heavy workload for the commander (which was an issue for French tanks as well).
Overall the German tanks were 'better' because they could be and were better lead, had more crew, better division of labour and greater tactical awareness.
Not exactly, the Germans also had radio shortages (this is what you get for having an electronics industry that is almost entirely just the "Siemens Company" and having the director of the said company be very anti-Nazi), but they did at least try to have a receiver for each tank and they pioneered some command vehicles with lots of radios that served battalion or higher level command. The mobile command vehicle thing I think is really the more novel bit, as I don't see similar vehicles in the French or Soviet OOBs.
The bigger issue for the French and Russian tanks (both of whom actually did have radios and radio receivers with more of their tanks than History Channel claims) was having the same guy be the commander and gunner, which is going to destroy situational awareness and make company-level coordination near impossible even with a radio ("Can't talk to you Captain, I'm busy shooting at the Panzer III in front of me!").
The French in particular expected each tank to fight independently for the most part, albeit when you're talking about having only 12 tanks to face a Panzer Division because the rest are stuck in Belgium on a fool's errand you can't really do very much even with more coordination.