Hi Chas,
Yes, it has happened to me about 3 times in the year I have had the laptop...Dell Inspiron.....when trying to restart.....not on a full shutdown.....My Daughter , who turned me on to the laptop and has one herself, told me to do this when freezing on restart. She said that's what they do when it happens and it works for them as well.
IMO if you want to run the battery down, I would do it while using the pc, but it would drive me nuts to have it run down while frozen. There's no particular technical knowledge behind my feeling, just a personal thing....