I come from a mountain biking background. Larger diameter spindles than square taper allowed for stronger crank arms and bottom brackets, which take mich more abuse in offroad scenarios than on the road. Larger diameter spindles led to smaller bearings (in the standard 68mm shell). The smaller bearings were terrible and did not last long. The next evolutionary step was external bearings: larger bearings than could fit i side a 68mm shell. Now we are looking at new bb shell sizes.

Does this make a notecable difference for most road bike builds? No. It is/was a huge step in the mountain bike world (imo).