Yup. I found tons of different definitions and recipes.....and opinions, of course.may be another of those generic terms that mean different things to different people.
Yes, acid(usually vinegar) will speed and improve(?) the breakdown of the bones.
It's about collagen, which is what makes it gelatinous, so different 'parts'(like chicken feet) can much improve that aspect.
Supposedly, true bone broth will stay viscous at room temperature.
As far as I'm concerned, if you cook those bones down for a few(or many) hours it's bone broth, tasty, and nutritious.<shrugs>