There's supposedly a 13th "secret" ending in which McCoy betrays the reps in the Moonbus and when he goes out is congratulated by Steele. Has anyone verified this? To be able to meet the reps in the Moonbus you'll have to follow the rep sympathiser path and therefore Steele has to die. I don't know how you can trick the game otherwise.

As far as I can tell (as part of the dev team for the Blade Runner engine in ScummVM) this path cannot be triggered.

Meaning the ending part that Steele congratulates McCoy for betraying all the Replicants on the moonbus. This special ending has been mentioned a few times by Louis Castle (he also briefly talks about this in the Ars Technica War Stories video which was posted early last year). The actual dialogue is a bit different than what Louis Castle describes, but the gist of it is similar.

There is a plan to at least try to restore this in the Restored Content mode, and I have some ideas how to go about it, but there are still some inconsistencies that I don't like.

What Steele is supposed to say in this case is actually addition to what she says in the Steele ending.
The extra dialogue is this (spoilers!):
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S: I gotta admit. I had my doubts about you.
M: What are you saying, Steele? You still wanna put me on the Machine?
S: Take it easy, will ya?
M: I plan to. I’m going home.
S: I gotta say, McCoy. You had me fooled. I thought for sure you were a Rep. Don’t get me wrong. I mean, you’re one crazy dude. But I like that.