Answer :
I think the writer suggests tying knots because you have to be very precise, so you would not mess it up, like if you pick a strawberry wrong and it bruises.
Knots usually take 1 minute or so to do. If you keep on tying the knots and get used to the pattern, you will get faster and faster and eventually will be able to do it in 4 seconds. It is kind of like picking strawberries. If you keep on picking strawberries and timing yourself, you will get faster like when you typed the knot