Didn't know if this was intentional or not, correct me if it is.
While reloading a MP5, the charging handle is always pulled even when there's still a bullet in the chamber / magazine.
I admit the HK slap is cool and all and you could see it on every reload sounds perky, but that also means the gun could not perform tactical reloads thus doing a full reload every single time.
Gun anatomy wise, you lose a bullet every time when there are still bullets in the chamber. Making it complete nonsensical to practice.
For comparison, the Kriss Vector doesn't have this behavior, Quick-A mags are used in both demonstrations.