I usually lurk here but I'll jump in. I'm a New England instructor who usually teaches adults, both never-evers and lower intermediates.
That first lesson for never-evers is not usually the place for hockey stops. Many people are in ill-fitting rental boots. They can't even side-slip with a feeling of security because their feet slide all around inside the boot as they try. Tipping the skis downhill to almost flat so they can sideslip in a controlled fashion, then tipping them back uphill again to get grip and stop can be very difficult because they have air above their instep and to the sides of their feet. This air makes their feet slide sideways inside the boot the whole time they are trying the exercise. Add some fore-aft slop in their boots and then they feel like they are going to slide out of control either forwards or backwards, and they are right. With beginners who can't sideslip (or side-step!) you can often blame the boot fit.
Hockey stops are out of the question for other reasons, though, in that first lesson. Achieving upper-lower body separation is very difficult for brand new skiers. If I had an all-day lesson with these folks, and if they were in snug boots, I could maybe do it. But with a 1 1/2 hour beginner lesson (what I have to work with) it's probably not going to happen. It would be wrong to teach inadequate hockey stops to someone who did not have the upper-lower body separation in place. (Hockey players, figure skaters, inline skaters, and dancers are a different story.)
When I teach lower intermediates, in my initial assessment I often ask them if they can do a hockey stop. If they say yes, I have them show me. More often than not they are using upper body rotation, and their "hockey stop" includes travel left or right. So we work on separation for the rest of the lesson, and if that clicks before the lesson ends, I go the sideslip route to hockey stops. When they get it, it's a big light-bulb moment and cements in place the value of making turns with the separation. They can feel the extra power of leg action when it happens without the turning of the torso.