Have you read any of the explanations about how QA works, deferments, or the explanation of why bug free updates are impossible? I'm not assuming anything. Based on their explanations, It's kind of insane not to conclude that they thought a bug free update is impossible. I mean... that's what they said.. If they thought it was possible (contrary to what they went to great lengths to explain), then they didn't deliver. If they thought it wasn't, which is exactly what they've explained, then they shouldn't have told us that's what we could expect.
Yes, I've read Tsuki's in dept explanation of how Q&A works, and not only do I agree with it, I can actually verify it. I study Game Development and make games myself, I think I have a fair picture of how our industry works.
We can not run a scanner over our games that picks out all the bugs, simply because such a scanner doesn't exist. Computers are stupid, they only do what you tell them to do, they can't tell if you're doing too little damage, or if you're not supposed to ride a minecart on grass, to name some fictional examples. If we code something, we
expect it will work, we don't
know it will. And if ten out of fifty interactions breaks something and we test it five times, chances are we won't find the bug, and our players (which, in the case of Terraria number a multiple of thousand, perhaps even ten thousand) will.
I do not for a moment believe that 505
or Codeglue promised you a 100% bug free game, I do believe they promised you a playable game that's worth the money they asked for it (which in my admittedly irrelevant opinion is very low to begin with). If you want to attribute their inability to do so, would you consider it as such, to malicious intent, I'm going to have to disagree with you simply to defend the honour of my profession.