GDP doesn’t include capital gains. Actually income and GDP should be equal if they are calculated correctly, so the 10% gap is probably just an accounting error.
Correct that it doesn't include capital gains, but it does include business profits... and in the long term those average out to be the same.
Similar to how it doesn't include housing appreciation, but does include imputed rent... in the long term rents and the cost of a house will track each other as well, just sometimes for even maybe a decade one surges ahead of the other.
As the other comment mentioned GDP per capita includes non-wage things like imputed rents and business profits so wages are not supposed to be equal to GDP per capita. You absolutely can use the difference between them to measure how much money goes to capital instead of labour.
