Indeed. I don't expect any judge would create case law along the lines of "no compensation due to extraordinary circumstances, but instead due to a failure to rebook on a competing airline that would have arrived a few hours earlier therefore creating a theoretical delay covered by compensation, assuming that other airline actually had seats available"

The only cases that make it to court - actual court, not just small claims procedures - are really about rectifying airline "abuses", such as LCCs charging to use the overhead bins or totally refusing to pay compensation that is clearly due.