Why don’t all the characters that are from the Old Republic getting the tag? Looking in the direction of the Triumvirate and other three sith lackeys (Marauder, Assassin and Trooper)
You could ask the same question for other characters/factions. I still argue that Old Ben did less for the rebellion than veteran smugglers Han and Chewie did for the resistance, but the vets are not part of the resistance and Old Ben is a rebel (with synergy for rebels).