not really, since he stated MAX height and MAX range (meaning angle=90 and 45 degrees respectively)
using 45 degrees to get the maximum range is only true if the landing position is at the same altitude as the launch position, so using 45 degrees will not always yield the max range in all situations. ie when projectile is fired from a cliff.
lets assume an axis where the base of the cliff is the origin,
this is the range formula for a projectile landing at the same altitude, maximise it using calculus will give you 45 degrees, telling you to launch at 45 degrees to get max range..
but this is the range formula in general
where d is height of the cliff, and maximising this is harder, requiring chain rule and product rule
being lazy and using a math package,
i got 4195 as the range.. and 43 degrees launch angle