I agree. To me this is very evocative of the pixel-art/retro look, even moreso than the low-poly Doom/Wolfenstein look.
The example from Back To Saturn X2 can be played on a software rendered engine with no concept of polygons at all.
2.5D would be the semi top down games such as most beatem-ups allowing you to roam around instead of just going left/right as the typical platform or action game, or most SNES RPG's.