It seems silly to me. The rocks don’t look like they’re made of plastic so unless someone already knows about them or finds a plaque to read about them they’re just going to assume that they’re big rocks. Which are pretty enough, don’t get me wrong, but rocks made of rock are also pretty, won’t potentially seep micro plastics into the ground, and don’t cost 100k a piece. If the point was to show off what can be made with recycled plastic, making something that looks naturally occurring and visually hiding the fact that it’s plastic is an odd way to do it.