I did some research on the super-size snowman phenomenon. Different types of snowmen go on different snow piles. When you're ready to build it, the ones that correspond to your snowman are enabled.
There are two spots that will build a super-size Broken Snowman and a super-size Classy Snowman, respectively. They seem to get scaled to the same height, so the shorter Broken Snowman ends up more massive. I don't know if the other kinds of snowmen also have super-size locations. If you think you've seen other ones, let me know and I'll see if I can find them.
Here is the rear view to show where they are:
This shows the snow piles: