1GR-FE Engine Cover - Why does this cut out exist?

You can see from the injection mold that they obviously added more height to that region so it wasn't for clearance purposes.

And if one were to undo that connector, it would just be easier to undo the 2 acorn nuts holding the cover on in the first place.

 

Good question, maybe just a visual inspection port?

 

Just went and checked under the hood. Same opening on my 2014.
I did just do my MAF and throttle body... is that the MAF plug? If so, why the port?

 

That is the MAF connector.

Just remove the 2 acorn nuts and the cover will pivot at the rear. A firm tug will release the pivot, then the cover can be removed.

There are no electrical connections on the cover.

 

Plain and simple. Access port.