3D Extrude pops your word forward and grows a deep solid shadow behind it, so the letters read as blocks with real thickness rather than flat type with a drop shadow.
A single ex-in keyframe scales the word up while the extrusion depth grows with it — the shadow is a stack of offset copies rather than a blur, which is what makes the side of the letter look like a surface instead of a smear.
Same family, different pacing. 3D Extrude arrives already deep. Monolith pops in flat and then grows the extrusion as a separate beat, so the depth is the reveal rather than the starting state.