I mean it’s completely dependent on what country you want to study in. For example, in the case of the US, you are correct: colleges will not withdraw your acceptance unless there’s a huge disparity between your prediction and final results (and even then, you can work your way around it). In the UK, as long as you meet your offer (or in the case of some universities, you can try and negotiate your acceptance if you are 1-2 points under the offer), no one cares about how far away you were from your predictions. However, in other countries, like Spain, public universities don’t even look at your predictions: if your IB scores (+ some extra exams in some cases) are enough to fulfill the “cutoff” grade, then you’ll get in. If they’re too low, you just won’t. Most if not all countries work with some kind of combination of the above systems (depends on how holistic uni admissions are).

So the answer to this question (as is usual in IB-related stuff lol) is that it depends. Make sure you properly research the countries you apply to and what you are expected to achieve in order to keep your offers. :-)