Rear main seal ???

[beamR X]

So I'm doing the clutch job and the VC in the transfer case on the iX.

Since my Tcase is sporting a new VC as of this weekend, I got motivated last nigth to do the dinky things that I dreaded doing because it was cold.
I puled out the pilot bearing and went on to replacing the rear main seal.

I pulled part 2 off (the seal housing, if you may...) to drive the gasket out. (part 5).

Here is my question:
I do not have the part 1 (didn't order), so I know I need it that's obvious, but what puzzles me is that the bottom of part 2 that sort of seats on the top of the oil pan is a machined surface as well, however I find no resedue of a gasket, nor does this picture show one...

To me it looks like this surface would leak if not sealed.
I do not understand how the face of part 2 needs a gasket against the block, but the bottom doesn't against the oil pan.
Is it because the aluminum against iron needs the gasket but aluminum against aluminum will seal??? What am I missing?

[PУCCKAЯ_e30ka]

order oil pan gasket and change it. You supposed to find "its" residue.. but since the car is pretty old, it might not even be there(like mine) You can also use some kind of hi-temp sealant.

[nando]

the ix does not have an oil pan gasket. you need a special sealant, you can use RTV but I don't know how long it will hold.

[beamR X]

the ix does not have an oil pan gasket. you need a special sealant, you can use RTV but I don't know how long it will hold.

That's pretty much what I did...
I put a film of gasket maker on it and will hope for the best. I mean... it looked like there was nothing there before.

BTW:
I had no idea an iX had no oil pan gaskets... Any idea why they opted for a "special sealant nando?

I guess it must have to do with torquing the pan to the block considering the front diff forces... I am just guessing, but I suppose the gasket would introduce "slop". Right?