Wasn't one of the reasons the mouse aim was so weird was because of the weird effect that would happen each time you looked up and down where the buildings would like they're insanely tall world tour fixes this by having real 3d which gives you the toggle to change between how the game originally looked to the real 3d look which makes look ing up and down less weirdy get it from pirat I mean buy it from steam
Basically, yes. Build was a raycaster engine and not a true polygonal 3D engine. Wolf3D was an early raycaster and very, very simple. I'll use it as an example on how weird(and fast!) these engines were.
Typical Wolf3D, amazing for its time.
Seen from above the map and player viewport of the above screenshot would look roughly like this. There's a slightly dotted line hitting the wall, that's a ray being cast.
Here's the trick. An engine like Wolf casts a simple ray, one per pixel of horizontal resolution, and when it hits a wall it calculates the distance between the origin(the eye/viewport) and the intersection(the wall). The longer the distance, the smaller the COLUMN have to be. The red in the image below would be the column drawn, the green line is my representation of the horizon.

You don't have to send 320x240 rays into the scene, one for each pixel, 320 rays(one per pixel of horizontal resolution) is enough because the horizon is fixed, 50% of a wall will always be above the horizon, 50% will be below the horizon, the length of the pixel column will be decided by distance travelled by the ray. This will always be true and it's a huge boon to performance.
Doom and Build are vastly more complicated than that but they're built around the idea of a fixed horizon at the center of the screen and if something can be assumed to always be true it can be precalculated or stuffed into a constant for calculations. Huge gains, brah. With some (very clever) modifications the player perspective can be moved up and down, like in Doom/Build, but the horizon is still fixed, it's built around it being fixed, that's why original Duke3D have that weird perspective warp to simulate looking up and down and it's why engines like that are called 2.5D.
edit: sort of like that, I'm going from old forgotten memories.