So on the left are 2 solar glass stacked on top of each other. They will only export power on the bottom side.

Placing another solar glass next to the functional glass makes it stop exporting power on the left side.

They will export power to the top though.

Also from the right side.

Tried it as a 3x3

From the top it will produce 37.5

From the bottom it produces 112.5 which is the correct amount.

From the side it also only produces 37.5

So the power pass through of the Solar Glass is wonky when going past a 1x1 setup.