Why Lie , Just to sound better???

Why does can am advertise that the 1000 xmr from 2016 comes with 30 inch tires when that is not true? The diamondbacks say 30 but they are only 28’s
I am looking at my rear tire to footwell gap and I don’t think a true 30 would even fit without rubbing.
What brought the whole (not a 30 ) to my attention is my son put some tires on his atv that say 28 on them and parked it beside my xmr and when you stand back and look it is crazy. My tires are only 1/4 inch taller And no my tires aren’t worn out. I only have 53 hrs on them. All in sand and mud or on grass. I do not run them on pavement at all

I guess my question besides why ? Would be will a true 30 fit ???