Would be surprised if that was necessary, Cape Town is at sea level and has 3.6km of runway. Maybe the journey was the other way round - JHB on a hot day?
Full power against the brakes is quite common with bigger turboprops at London City where they only have 1200m of runway to play with, especially on hot/windless days: KLM wind their Fokker 50s up to full power before brake release. They usually warn the pax that this is a standard procedure, though.
[This message has been edited by foghorn (edited 24 May 2001).]