To me, foldables are in the same category of "cute" device that will help you remember something. Yes, kids love them. They are easy. All these devices are colorful or cute or make a little rhyme or whatever. But like it or not, I feel that there's a tension between this aspect of math and the side where kids are grappling with rich problems, constructing meaning, and having ownership of ideas. I understand that many teachers use these "shortcuts" as ways to summarize a concept or wrap up a discovery lesson. And hardly anyone gets away from teaching any shortcuts whatsoever. Maybe that's not the point. But I do think that we need to think critically about what we're doing when we emphasize these shortcuts. Even if it comes at the end of a deep, rich lesson, there's going to be a bunch of kids that are going to remember the "trick" superficially, and it's going to be what the lesson was all about in their mind. It's going to train them, to some extent, to expect tricks like that in the future and avoid the harder work of understanding and internalizing the concepts underlying the shortcut.
Yes, a hook can be powerful for motivating student engagement. But I think it can also be junk food that distracts us from the substantive meal, which is not as shiny or easy to digest at first glance. Let's look instead for ways to make the mathematics more profound, more apparent, and more rich for kids. It really doesn't need to be dressed up and tricked out because it's pretty darn awesome on its own.