Rubbish. Insofar as Oxbridge is concerned, you need to meet the minimum requirement for your particular subject. For me, I took Law, the minimum prediction had to be 38. I was predicted a 38, I still made it to the Interview process, then lost out.
To get Oxbridge's attention, you have to have a lot more in your application than just an amazing prediction. Your Personal Statement has to be convincing and amazing, your recommendation equally good and you should have a certain amount of experience in your field (if it applies) and any relevant extra curriculars that you took.
A lot of people just concentrate on their academics and forgo all the other things they could do to seem like interesting applicants to Oxbridge. My Counsellor encouraged me to explore other options beyond academic clubs when I started the IB when I asked her for her advice on getting into Oxbridge. She told me that everyone who applies to Oxbridge has amazing grades, what do you have that is a cut above the rest to make you stand out and be called back for an interview?
Hope that helps,
Arrowhead.