Can place 2 metal extractors.

You can place 2 metal extractors on the same spot? One tier 1 and one tier 2. They just both fit in the same place? Is this intentional?

Yes, intentional. Notice how the icons fit nicely on top of each other? xD

Intentional, have a close look at the model, the t2 perfectly is build "around" the t1.

Yep!

Even the building models are designed to slot into one another!

This lets you build a round of T1 extractors before moving onto the more expensive T2 ones without having to micro the replacements!

I see.