Helping a child defuse by removing from a situation can be really really useful, but it is all context dependent of course. Sometimes what a child needs is some better ideas thrown at them, with the parent being really engaged with them. Sometimes they are having complete conniptions and actually really need gently removing from a completely overwhelming situation. It's a judgment call every time.
"I define time out as removing them from the situation, sitting in a calm, quiet place either next to or away from the adult until they have calmed down." as long as they get to choose whether or not to have the adult with them, I really really like your type of time out :)
"Then the adult explains why that behaviour is inappropriate and suggest that they apologise (but not force)."
Personally, I don't like forced apologies. I also think it's really important to remember that the adult viewpoint may be flawed. So often in a dispute between children, we don't get the back story (yes, X pushed Y, and Y is screaming, but actually Y had been bugging X for 15 minutes before hand etc etc). So I personally just try to make sure everyone is content, dealing with injuries first, but don't point fingers of blame.
If a child is ok with verbal explanations, then that sort of enculturation can be useful. For children who don't do well with language, or who have less developed social skills (young toddlers/ children on the spectrum etc), then I do a lot more through demonstration, redirection, or structural discipline. Rather than telling a child that we don't climb in the freezer, I would keep the freezer behind a locked door, or I would be with my child making it safe for them to have a really good freezer explore so that they themselves can either come to the conclusion that freezer exploration is rubbish, or they have a chance to persuade me that I was quite wrong in my assessment of the inappropriateness of freezer expeditions, or I would get something fabulously fun out to do instead
"Also what about the idea that if you ignore bad behaviour (as long as it doesn't hurt or destruct) it will stop as often the attention or reaction they receive from misbehaving is a reward to the child and unrewarded or ignored behaviour is less likely to recur and will eventually disappear."
I don't really buy into "bad" behaviour. There's always a back story. If a child is attention seeking, I wasn't managing to give them enough attention. If a child is climbing in dangerous ways, I need to provide better climbing possibilities, or engage them in deep pressure massage/pillow fights/ whatever they need to meet the sensory need. I don't think of children as being Bad. I think of them as knowledge-growing machines, whose attempts to understand the universe around them are not always convenient to adults. There's a mental switch which really helps me there.
NB I'm not really a UP devotee - I think Alfie Kohn hasn't really grasped the principle of adult fallibility, although there's certainly some nice tips in his writing which edge us towards being more child centred. I have got a LOT of valuable ideas from the Taking Children Seriously philosophy.