On the subject of late-notice or inappropriate practice engine failures this tale is many years old but almost certainly true and I believe more or less correctly related here, though doubtless others will correct any errors.
One day the CO and Senior Pilot of a certain RN training squadron were doing mutual instructor revalidations when, at almost zero airspeed and 100ft the pilot currently flying announced,"You have control" immediately followed by "Practice engine failure, Go!" as he rolled the throttle closed. The second pilot, not wishing to have the ensuing accident occur in his hands replied "Oh no you c***, you have control!" and put both hands up in the air to reinforce his point.
The affair did not end happily as even a Whirlwind could not cope with a stunt like that and the subsequent rancour between the two crew did little to enhance their personnel files I imagine.