Depends on what you're asking?
Is it true they are discussing highsides? YES
Is it true that one bike is easier to highside than any other? NO
Reasoning:
A highside is typically caused when a rider is leaned over in a turn, and as the rider is exiting the turn, they start to accellerate. This is where the
rider's mistake is usually made that causes the highside...NOT the bike's mistake.
As the bike is exiting the turn and the throttle is applied, torque is sent to rear wheel/tire. If the RIDER rolls on the throttle too fast or is not smooooth with the throttle, then it can cause the tire to lose its traction with the track/street surface. This in and of itself will not cause a high side. This is what causes the rear end to slide out, BUT... A highside will reasult if the rear is allowed to drift too far out of alignment with the front, and then traction is regained suddenly due to the rider backing out of the throttle too quickly. This is when the momentum of the bike is going sideways, and suddenly cannot go in that direction any longer. This is where centifugal force takes over and the bike is flipped over to its "HIGH" side subsequently (normally) launching the rider off the bike and into the air.
Throttle control and knowing the limits of your tires are the key to preventing a highside. I learned these limits at Road America when I had the rear tire break loose coming out of the last turn onto the main straight. It did not slide too far out before regaining traction, so all I felt was a quick wobble in the rear of the bike. It was enough to tell me I needed to be a little smoother coming out of the turns.
If you are smooth...dam smooth...then you can go from a steady throttle at the apex to full throttle at the exit of the turn (minimal lean angle) with no problems, but you have to be smooth.
Hope this helps