I think the root observation here comes from https://en.wikipedia.org/wiki/Fourth_power_law which really talks about the inferred stress to the road for given weight on the axle, not tire wear based on vehicle weight. The above seems to be using a simplification based on passenger cars staying with 4 tires across 2 axles but how this relates to tire wear is going to be a bit more complicated when you start talking about vehicles which can have more axles, more tires per axle, and significantly larger tires.

I'd believe buses have a lot of tire wear compared to an individual car but I wouldn't use that relation as proof of just how many times so.