Riddick bowe had a couple defenses against weak opposition before losing to Evander in their rematch. I think Lewis won a couple defenses too but not sure.
Liston did indeed kayo patterson easier the second time, I'm not really sure when all the split belts came into play. In fact, the first time I've read about the heavyweight title being fractured was during Ali's first reign, I think Terrel was the champ, but before that, I can't think of any talk of more than one champ per division. The belts didn't really become a huge hassle until the 80's, then, with all the talent around, they just as soon avoid the other belt holders and hold what they had for as long as possible. Generally, the longtime champs like Holmes, were accepted as the lineal champs even if they got stripped of a belt. Hagler is the only fighter who stood up to the orgs and kept his titles together.
Fighters also used the mandatories to preserve their records by avoiding a potential tough match, allowing themselves to be stripped and fighting a big money fight later. Michael Spinks avoided Tony Tucker that way, got stripped but went on to fight Mike Tyson for the big purse a little later. Bobby Chacon also made excuses not to fight the young, up and coming, Hector Camacho and was stripped of his title. In his case, he knew he was too old to beat Macho.