Yep, they are made of some kind of plastic resin that can be 3D printed. I don't know how much more durable it is, and/or how much more shock protective they are, if at all.
It's unlikely any of these earphones provide substantial shock protection for the BA drivers inside. If people are afraid of problems with durability of acrylic, such as in the OP, it's best if they avoid these "boutique" makers and go with manufacturers that can provide robust warranties that just replace everything at once. I personally don't think it's much of a problem, though, but that's one of the concerns the OP had.
Most don't shatter, unless you take a hammer to them (like Kunlun mentioned). At most, they crack, and in small spots. Most people also think cracks in the lacquer are cracks in the shell. Not so. The acrylic lacquer is more brittle than the acrylic wall itself, so the lacquer can crack due to thermal expansion, minor trauma, etc.
And for official record, FitEar IEMs are NOT filled with acrylic. It was a misconception that many of us (including me) believed years ago. It is not so. They fill the tip up to a certain line, but the drivers are not encased in acrylic. FitEar will lacquer on acrylic in areas they feel require reinforcement. However, I've seen an early model 333 crack near where the plastic faceplate and shell are joined.