Seeing only 4 games as all SOVs further illustrates my point that you only see heavy SOV loaded games at level 12 and down. It also shows that the level 12 and down players have the chances to win that I posted since the stats are ALL games.
Looking at all of the data and playing around with some ratios I do believe that 4xSoviets is probably the weakest matchup there is out there at the moment.
However, I am not sure if the 4x Setups is really what we should look at. Those matchups make up a very small part of all games (currently ~3% overall regarding all Soviet teams, which probably increases to whatever percent further down the ladder). I'd not subscribe to your "More soviets = lose." statement, not only because it is "too generalized", but also wrong in many parts.
There seems to be indication that adding a Soviet to a "pure" USF or pure UKF team brings down the win rate. In that regard, the statement is correct. However, adding a second or third Soviet does not do an awful lot. Only a pure Soviet team then again seems to be disfavoured.
Adding a Soviet to a mixed team of USF and UKF often even improves the winrate or does not really diminish it.
To make it short: We can only guess how many "all Soviet" games happen at the bottom of the ladder. However, they are very likely quite rare events. All Soviet teams are likely disfavoured, but it also seems to be unlikely that you get multiple of these games by random chance. I'd say the contribution of these specifically is probably rather low, especially considering that rank 12 is mid ladder and higher rankings go along with more even usage of all factions, thus less chance for all Soviet games.
It would be great to have some data that actually shows what we try to discuss here, at the moment we have to assume so many parameters and other factors that could play a role.