Yes, this applies to all the rigid coatings - fiberglass resin and epoxies (including Pond Armor). They need to be supported by a rigid surface underneath. So if you apply them over something flexible like silicone, the flex underneath will eventually cause them to crack. But silicone will adhere to cured epoxy so you can apply it over the epoxy.
Also, regarding Pond Armor, fiberglassing the corners is still recommended unless you build a strong external support frame.