I think I don't understand international upgrades, waitlists, etc. well enough to comprehend your explanations, good though they may be. Perhaps a real-world example would help me. (I know this will be painfully rudimentary for you Savvy-Platties, sorry. )

I am Silver Elite with 106,000 OnePass miles accumulated. I am booked on flight 56 from EWR to CDG on a 777. As I understand it, I can "pay" 20,000 miles to upgrade to BusinessFirst. If I do that, don't I get a seat in BusinessFirst? There's no waitlist involved, is there? And there are also no "free" upgrades on international flights, right? So, why/how would making a phantom reservation help me? And what does 3 days (72 hours) have to do with anything?