Neil Young himself is a draw for most people whether he's in Buffalo Springfield or playing with Crazy Horse. Just the drummer for The Police and Oysterhead is a draw to virtually no one, despite his respective bands being draws.
Yes. What's your point?
You're saying they'll bring someone back to headline a year later as a repeat for the band they're more known for. Your example and argument showing precedent of this is the drummer for The Police coming back one year later after playing with Oysterhead. Copeland coming back doesn't really affect or diminish whether most people want to see The Police the following year. He isn't the main draw of that band. Replace him with a fill in drummer for the night and the majority of people won't care enough for it to affect the show for them.
With Buffalo, Neil is the biggest name in it and people may feel they got their Neil fix through that. Not that I feel that way personally. Just saying that Neil two years in a row would be more noticeable as a "repeat" type of thing than The Police drummer showing up two years in a row playing a completely different type of music. Plus Buffalo did play Rocking in the Free World. I personally don't think Buffalo being there stops NY & CH from being booked this year, but your example didn't really work to show precedent being set.
I grew up in the 90s and I still have minimal excitement over RHCP. I've been listening to some stuff again though and there will be a few songs that'll be fun. Let's petition that drummer via Twitter to let fans choose their Roo setlist haha.
"In the darkness hundreds of glowsticks streaked the air like tracer shots in war. Giant inflatables bounced over dozens of light sabers pointed skyward. Stuffed animals impaled on sticks danced above the hot crowds, puppeted by someone just given ecstasy by a friend made seconds before."