Slim,
I never said never!
There is a difference between being shown what it all looks like when you go down below 500ft and what you do for recurrent training.
For a ME rating you do an engine shutdown and restart. When you are au fait with that you continue the rest of the training by flying with zero thrust after identifying and securing the 'dead' engine.
In a similar vein I think you can meaningfully train FLs between the altitude you have your simulated engine failure and 500ft.
If you do PFLs as often as I think is necessary to be proficient you will know whether you are in the groove by 500ft.
Not sure why you think flying a taildragger will make you better at doing a FL. See what you say about grass fields and people's lack of acquaintance with them. We had a thread not so long ago making that very obvious.
FD