I would say this is an example of what
@Russell Jones was talking about. Your confusion seems to stem at least in part (if not indeed, mostly) from not differentiating clearly between offside
position and offside
offence.
In your quoted post here, you are using the one term, "offside" to refer to both concepts, when in fact they are totally separate.
I think this can be illustrated (and hopefully elucidated) by the following re-wording:
"If a player is beyond the second last defender but doesnt receive or touch the ball, then he is in an
offside position but has not committed an
offside offence yet.
But if he retreats into his own half where he isn't in an
offside position, when he receives the ball he is guilty of an
offside offence (because that is where becomes involved in active play)."