Only to the extent that withheld labor during a strike affects it. Once the strike(s) are over, an economy that puts more spending money in more pockets will be a bigger one
It turns out that the size of the economy is related to how well-distributed the wealth in it is. If most of the money goes into wealthy pockets and everybody else lives in a sort of poverty-imposed austerity, that depresses a lot of that economy’s potential.
What the UAW are after is not a smaller economy, but a more-robust (likely larger) one that includes more people in it.