If you micro your m3 well it will outlive the kubel.
I guess him being N°1 on OKW/SU ladder doesn't have any relevance on what he is saying.
Kubel: 7.0 speed, 4.5 acceleration
M3: 7.3 spd, 2 acceleration
Equip 5% increase max speed on Kubel bulletin >>> M3 can't catch you up.
What he is saying is that if you are not caught by surprise by the M3 (check opponents base for tech) you shouldn't be losing your Kubel. It's a game of constant kitting where you pull backwards while getting fire support from your SP.