There is a bit of a quirk with this one. Whilst the inverter does only have 2 MPPT inputs, and normally you can only have panels facing the same direction using a single MPPT input (i.e panels facing only two different directions in total). However, if you have panels facing the opposite direction to each other (I.e east and west), these can also go into the same MPPT input.
Don’t ask me the technical reasons behind it, but it is a thing, you can see more here:
I was surprised to learn this recently, so I’m not surprised that the installer is not aware, but you could point them to this thread.
Hope that helps,
Marty