I understand your concerns but smooth-on is a US company so I don't think Gametoys will be using that, its most likely their own equivalent or better manufacturer available to them in China, which makes more financial sense for them.They said medical grade silica and not silicone. Queen studios and infinite claim medical grade as well for their silicone, but when people asked them what brand of medical grade silicone was used they were kicked out of the FB groups. A good test is to see if they take Psycho paints or not, but I'm not willing to lose a cloud for that. I'm not trying to be negative, I just have a hard time believing they used a company like smooth-on to source real medical grade.
The arms set are made from the same medical grade silica so that's one way to test if you want to.
We don't need to take their words for it but we also have to exercise a lot of common sense here. These are mixed media collectible figures and not really mass produced plastic Hasbro that can stand up to repeated, long term posing in a certain way. I don't mind the occasional dynamic poses but I would definitely think twice leaving them in that pose especially if multiple mixed media are touching each other in that pose. I know there are collectors who don't mind these dynamic poses so it's not a concern to them, especially if it can only be viewed at a certain angles.
The limit is yours to define.