I don't think a forced landing in an aeroplane bears much relationship to a field landing in a glider.
You've never flown a T21 then...
The language you use is very interesting and serves to illustrate a point. 'Forced' landing in a light aircraft and 'field' landing in a glider. Perhaps this is one of the main differences in mental approach. I wouldn't see a power off landing in a field other than the one you thought you were going to land in as any different to a field landing in a glider in a field other than the one you thought you were going to land in.
It's the 'Engine failure this is an emergency' mode that is the crux. It's not an emergency, it's an out of the normal situation that requires a field landing. If gliders land in fields because they have run out of sky why don't we call them forced landings? It's an aircraft, it's landing in a field, it's not where it intended to land. That's all.
Let's not split hairs here by the way, I'm talking about engine failure in the cruise over reasonable terrain (IE most of the UK) not an EFATO 200' up in the Rocky Mountains.