From personal experience, I crashed my poor old CB750 coming out of mechanic's garage on new set of tires. Rear wheel spun and slid like it was on ice.
A bit older and wiser, when I sat on my recently purchased SV650, used from the dealer but with brand new tires, I made sure to do a bunch of figure 8s in their parking lot, as well as braking. Rear tire would lock up almost immediately with rear brake, only after a little bit of riding and gradually putting more force into braking, did it stop locking up, and I was comfortable to get on the street on it.
OP you can listen to all experts in the world, but personal real life experience trumps them all.