One misconception about matcha is many think that matcha is produced from Gyokuro leaves. Matcha and Gyokuro tea leaves are grown in a similar way (shade grown) but they are processed in a different way.
Gyokuro is steamed, dried and rolled. Matcha is going through a refining process to remove the stems and veins, then dried to produce Tencha. Tencha is then ground into powder to create matcha.
Both Gyokuro and Matcha has good umami and low astringency. The shade grown process suppress the astringency and increate the L-theanine of the tea leaves. Gyokuro and matcha are similar in several ways, but they are different product.
Sencha, is not shade grown. Therefore, Sencha has higher astringency and lower L-theanine. The astringency of Sencha actually gives it the refreshing flavor. Powder made from Sencha can't be labelled as Matcha, it's only green tea powder but not matcha. Many shops sell green tea powder as matcha, it's important for customer to understand the differences.