After some sleuthing, it seems forums member Derik has answered my question of who "Skipjack" is. https://www.editorsguild.com/FromtheGuild.cfm?FromTheGuildid=84 According to that article, the red Rampage is actually Skipjack, which means two things - that both sets of repaints now have names, and that Starscream's line ("Rampage, spring the trap!") is an error much like Brawl/Devy in the first film! This explains Skipjack's name being listed as a voice credit, but not Rampage's. It also explains the name given to the yellow figure of Rampage.