Yup, that's what I used to get the number - along with an addon that saves all the data from different characters and sums up the played time of all of them. Last time I checked it showed over 1200 days (=28 800 hours) for me - but it's been a while since I checked the total, and it doesn't include characters in Classic (or deleted characters). So I just rounded it to 30k hours, close enough.
My most played character is my shaman, with 450 days (~11k hours) played - it was my main character from TBC to WoD (from 2007 to early 2015). Current main is Druid with 240 days (~6k hours). So these two characters alone are more than half of my total played time. :D
Vast majority of it is active playing - I've thought about this earlier too, and I really rarely just afk or stand around while in game. Even if I'm just waiting for eg. raid to start, I usually just go do some gathering, pet battles, dailies, something.