More than velocity, continuing to respond (from uke) is important. If I punch at full speed, but still leave my arm out once it's intercepted, all my partner needs is a decent block and the rest is easy. If I pull my arm back, follow up with a second attack, etc., they have to learn to find the right opening, rather than expecting the right opening off every attack.The hanging of a punch lol that early on in any training
You can very easily progress from there by increasing velocity and in my art that is actually very important if you really want to start learning and not have your uke help you out