No I don't think it was a mistake. I don't remember that question on respiration in yeast, although I do remember there being a 4-mark question on fungi, so maybe that was it?
The thing is about respiration is it is such a hugely fundamental part of biology that it's just completely insane to me that edexcel thought it was a good idea to take it out. It almost seems to make sense that, if they have slipped up, that is how they've done it.
I also found the paper hard, and I relied mainly on the advanced info too, but it was difficult because there were so many 3 and above mark questions that made the paper really awkward to navigate.
The questions did match up to the advances info, just not how anyone expected. Let me give you some examples. Selective breeding ended up being about crops, but most people were expecting to answer a question on selective breeding on animals. Reproduction ended up being in plants, instead of humans. They asked some rogue questions on the Inheritance topic that no one saw coming because it's never really been assessed (mainly thinking about that question where the answer was "polygenous" - 3.22 in the spec). The only thing that seemed to be what was expected was Coordination and Response. However, everything on the AI that edexcel said would be on the paper was, in some form, on the paper. They didn't make a mistake with it - they made the paper harder so they would still be able to differentiate students. Otherwise everyone would get 9s, or they would have to make the grade boundaries ridiculously high.
AQA are a bit weird anyway because they, at least for Computer Science, hedged their bets completely with the advanced info - what we got was a load of rubbish where they said that basically there was no guarantee that what was written on the advanced information would 100% be on the exam, and that you should learn everything anyway, on the off chance that basically anything else on the spec might be in it. So I'm not particularly surprised to find that it's AQA everyone is saying messed up.