That's a pretty good observation.
I wouldn't count The Rock 'n' Sock Connection or The Brothers of Destruction. I'd only count tag teams that were put together to be a tag team, and not singles wrestlers. The Undertaker and The Big Show (to my understanding) where always in the WWE Championship division, while The Rock and Mankind were sort of on and off from memory. Kane and The Undertaker teamed, but it was more to be a force than a tag team.
Bradshaw and Faarooq were teamed because they had nowhere else to go. So yeah, to memory, only the APA were a tag team that was focused on the tag team division for a long-time as a real tag team that won tag titles and have both held World Titles.