The Fiestas that I had as AA school cars, were always quite enthusiastic with the stop/start. Engine would be barely warming up, and the system would cut the engine, which would be a problem in winter, when you are wanting some heat inside.
Conversely, there appeared to be no connection between the stop/start system and the engine management. With a turbo, it is a good idea to let the turbo spin down before stopping the engine, but coming to a stop from a fast run, with the turbo still spinning, it would stop. Not good for turbo longevity.
Having said that, the Fabia does not wait either, so there's room for improvement for all.
First bit sounds like good old Ford engineering striking again.
PSA stop start one of the conditions is "is the cabin at the requested temperature"..so if the cabin is cold it doesn't turn off. If it is it turns the fan down slightly while the engine is off so it doesn't drain the battery...or take all the heat out of the coolant, it then uses previously auxiliary pump to circulate coolant while engine is off so it doesn't just take the heat out of whatever is in the heater matrix.
Regards the second bit, I'd assume you'd have coasted down off throttle before stopping so it's unlikely to be running the turbo above idle speed as you come to a halt. Yes...Ford should use the auxiliary pump to cool it while the engine is off...but sounds like they don't.
To be fair if I don't want the stop start to operate there's 2 easy ways...press demist or put a quarter turn on the wheel. Both should in most cars stop it.