Is there a reason that Depots,, which are 3x3, can NOT be inserted Out of (and into) the very center tile of that 3x3 space?

In Nullius, earlier game, the inserters can only carry one item per insertion/extraction. So, you have to gang them in groups to allow faster throughput of stuff into and out of things. And with capability of switching any of those inserters between reg and long, you can use a 2x2 array of those inserters to give you 4 times the throughput of stuff.

But, for some reason, the center tile of the Depots can NOT be inserted in/out of. Because of this, with an array of 4 inserters, only 3 of them are running and the 4th one is "Waiting for Source Item" or "Target Full", depending on the direction of insertion.

Is there a reason for this?

I've been thinking about that a little. The center tile is the drone storage. I noticed when drones were being unloaded onto some belts.

Could that be in one of the two road facing corners, flippable?? and something on the roof to make the square that you can't in/out from/to...

or the center roadside one?

And good thing that I was using filters on those inserters.