Earth's surface isn't a microgravity environment. The principle that you can get purer crystalline structures with less interference from the earth's gravitational pull has explored on space stations since the 1970s; that aspect and potential applications in higher performing semiconductors and drugs are fairly well understood

What hasn't been solved yet and Space Forge (and Varda et al for biotech) are hoping to solve are the unit economics of reentry vehicles to actually make it viable for manufacturing.