They aren't like an Anubias to that extent. Cryptocorynes will grow roots several inches under the gravel.You see the part where it turns from white to woody? You want the brownish part submerged in the substrate. If it loses its leaves after a few days, don't despair, Crypts are known for this. After they melt away, they should come back. Changes in lighting and water parameters make old growth leaves drop sometimes.
Nothing good happens fast in an ecosystem.