If all villains will really come to Ultra Sun/Ultra Moon dimension from a dimension where they reached their goals, this poster makes sense.
If they reached their goals that means that all teams caught the legendary that they were looking for.

>Team Rocket never looked for Mewtwo, Lugia or Ho-Oh
>Team Aqua and Team Magma never looked for Rayquaza
>Team Galaxy never looked for Giratina
>In a dimension where Ghetsis has reached his goal the first time he tried (in a Black/White timeline, not B2/W2), he caught Zecrom/Reshiram so there wasn't a reason to catch also Kyurem
>No evil team tried to catch Zygarde