It’s essentially a drop in replacement for an LM7805 (linear regulator) but is switching so won’t melt when you have to step down a high input voltage.
Seems like the kind of thing a lot of hobbyists would go for, and their international shipping rates are too crazy for me to order directly from them.
I think the point is to use a switcher, not a linear. There are many cases where a linear won’t work well. Even at modest current draw a linear will require a heat sink when the voltage drop is large enough.