I read somewhere that GOP candidates collectively got more voters than Democrat candidates on Election Day in Virginia, and that the now-Democratic control of the legislature is really just a function of how the districts are arranged.
I think I read somewhere that a number like you suggest excluded the uncontested races.
I made a slightly similar argument about the 2018 turnout, saying that the Democrats winning the popular vote in 2018 was meaningless because they were defending 23 Senate seats to the Republicans' 12, meaning they'd naturally have a higher popular vote because they had more elections.
It would seem that in Virginia, Democrats would also win the popular vote if Republicans don't even field candidates in a quarter of the races.
-PJ