Your sleeve cap actually should not be the same depth as your armhole! To fit together perfectly, a sleeve cap and armhole must have the same perimeter. Think of a little ant crawling around the armhole, and over the top of the sleeve cap from bind-off to bind-off. Those two distances must be equal for the sleeve to fit in nicely.
When you block your sweater pieces, please avoid the temptation to stretch your sleeve cap to the same height as the armhole! Your fronts and back will match the armhole depth on the schematic or the "actual measurements" section, and your sleeve cap will match the cap height designated in your sleeve’s "actual measurements" section. They should not require aggressive blocking or pinning to reach these measurements.