This is one thing that never made sense. You get a $10 meal in a cheap diner with excellent service, 30% tip! $3. Crappy service at an upscale restaurant, only tip 15% for that lousy server who served your $75 meal! $11.25. So you pay almost 4x as much for awful service as you would for excellent service, just because of the menu prices. The myth that tipping rates are based on quality of service falls flat when we base it on a percentage of the bill.
Pragmatically, it’s what we ended up with because previous generations set it up, so we’re stuck with it until someone successfully eliminates it, but no part of it makes any sense whatsoever, so as long as it’s all babbling nonsense, really any argument from any viewpoint is relatively valid.
Back on topic, tricking people with fake money is obnoxious. If someone wants to give a nice quote, better to leave a fortune cookie. Or better - a fortune cookie, a lottery ticket, and a thank you note. Probably not what the server wanted, but nicer than a fake $20 smeared in holier-than-thou judgment.