You got it right. In my home they didn't run any cat5. They used the rg6 that was already here. Why would they spend all that extra money running cat5 when they can use the cables that are already there? AT&T was smart enough to figure a way to retro fit the existing wiring to save time and money. If the wiring is bad or out dated then they spend 4-5 hours on a install running all new lines. AT&T has been around a long time for a reason!
This is CABL.com posting #248603. Tiny Link: cabl.co/mbcPT