Dear Lord kid, the QA Team is the one that does the official testing as well as the betas.
Not to mention they didn't even say MP is good for hunting bugs but for hunting exploits (which is design flaws that players can use to get unintended features). At least learn the terminology before talking about how one should do their QA -_-;
The "QA team" is like 2 people.
And I was talking about exploits. For example, in CK2, the ability to simply play with no vassals by mass banishing and imprisoning people. Or in EU4, the ability to change governments at will by forcing OPMs to "accept tribute" of government changes, or to nuke your AE at will by forcing them to "accept tribute" of another OPM's release. Or any of the thousand things DDRJake used in his Ryukyu WC, unless they're going to say they never played MP before the game was released.
There's plenty of others - like building 100 temples before westernizing, then immediately canceling them all. The kind of stuff you'd never discover in MP.