Michael - I was not there and you were, so I cannot be sure BUT I think it UNLIKELY that the pilot selected 'take-off' power at 45 deg to the runway.
More likely he/she had been asked to 'expedite' take-off and was on a high-speed 'slip' and 'stood-up' the throttles to the 40% normally used before rolling (see other threads on PPrune) and then fairly quickly up to take-off power. THIS is not dangerous and is also not that uncommon. Being at full power at 45 deg IS dangerous!