OP, my educated opinion is that breaking in an engine “may be unnecessary” but cannot hurt anything. Therefore, it may prevent premature issues down the road, and is a VERY easy and cheap way to possibly prevent problems.
186 miles and no hard braking, then another 314 miles before I could tow, and then after another 121 miles I can finally drive at my normal speed.
Boy, do those engineers have this break-in down to an exact science! If I were to buy one of these new I'd be watching that odometer more closely than the speedometer for the first 621 miles. Then I could change the oil every 10k and run the transmission fluid for the lifetime of the (vehicle? transmission? you decide!), and drive the snot out of it going forward.