I fondly remember my ME instructor!
We did airwork during night-flights ( "do you think stalls only occur in sunshine amigo?)
On final, he had the habit of just turning the fuel selector off on one engine, saying nothing... I sure learned how to identify a real engine failure... (also, he forbade me to feather while on final approach if glide-path and blue line could be kept. )
During my first hour, he gave me an engine failure (at 4000') in the hold, in IMC (night) where I had to complete the drills including feathering and restarting.
Conclusion, yes, some might consider this "dangerous", but it made me a better pilot. He knew what he was doing (4000h multi-instructor, JAA CPL/ME examiner).
Oh, and all on a Seneca1!