Don't understand. Microgreens are super baby leaves of lettuce and other greens, I believe. I'm not sure what 'packs' you are talking about. Please be more specific.

Probably not, if I understand your question. It would be very inefficient for most growers to grow directly in the clamshell, and a huge waste of packaging material, since you could fit more in the package than would grow. Some restaurant chefs prefer to buy them that way, in order to cut them fresh and thus gain some shelf-life, but retail would be more likely to be harvested from the growing flats and packaged.