“Reasonably square” from the factory could mean suspension mounting points that differ by an 1/8” side to side. If you try to correct that with a strut rod, you will get binding.
When you set the alignment on your car do you set one side and then just copy the camber bolt positions on the other side and call it good? No, you set the alignment on both sides to get the same final alignment specs. Same deal with the strut rods. Sure, the lengths should be fairly close from one side to the other, just like the camber bolt positions. But more likely than not they won’t be identical. The actual length of the strut rod is less important than getting the LCA to move without binding. You have to do the length setting process on both sides independently.