I assume that you do not understand the definition of "wear". Obviously it can happen from contamination. But contamination aside, roller bearing failure modes do not include wear. Overloading or overlife use failures are from fatigue of the metal which leads to spalling of the surface. To the untrained, this may appear to be wear. Bearings are sized to a load and life that will leave them unchanged through their life period and will show not change in dimensions unless this load or life is exceeded as long as the lubricant is maintained and not contaminated. There is no "wear" of the parts.
As to the design change shown above, they most likely changed as it is easier to setup the taper roller bearings. There is little thrust load, so the benefit is little from a bearing loading perspective.