1. Blizzard doesn't really discuss the specifics of how an important game system works behind the scenes. Claiming to know how their system works is kind of LOL and empty.
2. There have been recent changes to the queue system, including the prioritization of specific roles. If you don't have role parity on each side then you're sitting in queue until you do. The system also prioritizes Battlegroups. So when it has to pull people from outside a battlegroup, it takes longer to pop.
3. If people are used to wargames giving instant pops, that's because wargames are different than random queues, and you should not expect random queues to be instant, ever.
4. We don't know if all 20 people (given role parity between factions) stayed in queue, did not do skirms while waiting, or weren't doing other random things like going afk or logging on/off between toons.
I get it that sometimes things get bugged, sometimes Blizzard doesn't do a very good job of addressing obvious issues. I want to agree with this thread, but more information is needed.