I'm with letMfly on this one. Everyone knew from an early age that this was a dangerous practice because Biggles said so, and he should know. Imagine my surprise on starting a twin rating course to find the chief instructor at London Flight Centre (Lydd) had never even heard of this advice!. Mind you, he was a gash hand anyway.
Evidently years ago there was likely not to be enough rudder authority to overcome the asymmetric torque and the thrust of the good engine on the outside of a turn could roll you over. I bet Wellingtons and Beauforts and suchlike did this.
A go around in a Seneca can require some wing down to assist the rudder if I remember right, so clearly there is aturning moment at high poweer that the rudder alone cannot cope with. Imagine the result if you needed sustained go around power in a turn (perhaps to avoid terrain) and you were already turning the "wrong" way. Perhaps it is good advice after all. Certainly sounds like good airmanship to consider it?