Mine would always just pick one thing and really drive it home, like it was "the day's lesson, or something." I mean, I guess it was. Like, "if you step inside my stance, you'll land on your butt, today," or sometimes, "every time you throw a flashy kick above the waist, I'm gonna spin you and drop you," or maybe, "if you duck too far forward and down, you'll regreeeet it."
Depending which of the three instructors it was, it was always different things, done in a different manner, but the pattern was similar. Sparring sessions should always be lessons, especially when the skill set is mismatched.
I can honestly say that I've never sparred with an instructor from my school (or any other school) and experienced anything much like this sort of toying. I can think of several instructors, in my school and out that certainly can toy with me like that, and they certainly don't hesitate to really dominate sparring, but there's always a point outside of showing who's better.
I think you should always try to emulate that restraint and teaching mentality when sparring with someone below your level. Sure, if they're flinch-happy, maybe make a point of really pressing them with head-level strikes and attacks, but if they're lacking forward momentum, perhaps telling them to just go for it, and then playing mainly defense yourself makes sense.