I find it hard to accept that a game, that truly uses 3D to create a 3D effect shouldn't be true 3D.
Your definition of "true" actually seems to be "complete", which I could have agreed to, but is a) black/white logic and b) still not the case today. There are still 2D techniques in use to create or support a 3D appearence. So we're discussing the point when it's enough 3D to call it "true" 3D? What was the beginning of that discussion? We spoke about 3D open world and I think in this context Vindicator was still correct with his mention of UU.
UU doesn't truly use 3D. That's the part you seem to have a hard time understanding. It might have texture mapped walls and ceilings, but the characters and objects don't have real 3D models. It has 3D rooms with a bunch of 2D sprites walking around in them.
I'm talking about a fully 3D game using a 3D engine, which UU is not. You're talking about 3D "effects" which was obvious from the start of this discussion. Creating the perception of 3D doesn't make something fully 3D. UU is a mostly 2D game, that's all I'm saying, and that's what I've been saying from the beginning.