A beginner should learn to execute perfectly those basic lifts:
Power clean from hang
Power snatch from hang
He should strive to use more weight over time, but not at the expense of proper form. Obviously with movements like the power clean, power snatch and push press the explosiveness is built-in, so you have more leeway for the other exercises when it comes to speed of movement.
I accept a slower rep speed on the basic strength moves (squat, deadlift, bench press, pull-ups) as long as form doesn’t break down. With a beginner grinding will thus not be allowed because 90% of the beginners break form once they start to grind. But it is NOT the grinding that is to be avoided, rather the break in form.