Yes swopping from bike to bike can catch you out if you're not used to it.
That shows a lack of duty of care from the sales guy! He should have reminded you to test out the handling and the brakes before letting you start off!
If you hire a bike from Eagle Rider they advise you not to leave the car park until you've ridden a couple of circuits around it to allow you to get a feel for the handling. They have many storys of "experienced riders" getting into difficulty.
I change bikes regulary and every bike behaves differently even if they are the same model.
Clutch biting point, brakes, long or short wheel base, forward controls etc it all adds to the excitment.
I led a short group ride for a Harley experience demo ride, "experienced riders" wanting to try one. Even with a detailed briefing before we started one rider go into difficutly because his bike ( XR1200X ) brakes were much sharper than he expected! He applied a fistful of brake on a bend.
Everything that passes an MOT is deemed safe, but they still handle differently
