Chicken texture: Store Rotisserie v. Pressure Cooker
You're comparing two completely different cooking methods, so it's no surprise that there would be a difference.  A pressure cooker is a sealed vessel which retains the moisture in the cooked food, except for any steam that's vented off.  By contrast, rotisserie is a form of roasting, done by definition over a heat source or within an oven, but not sealed.

Rotisserie roasting is great in that it allows the food to baste itself, but there is inevitably some moisture loss as juices drip away from the meat, certainly much more so than in pressure cooking.  That's what contributes to the drier texture of the rotisserie chicken.  The breast meat will also dry out more quickly than the darker thighs and legs, but big markets want to minimize any food safety concerns, so they're probably playing it safe and cooking the chicken to a point above its minimum internal temperature.

So no, they're not doing anything wrong, but they are using a different cooking method than your pressure-cooked chicken, with predictably different results.