His tutor isn't correct IMO. He should try for 1-2 aspirational, IMO, and the rest at the level he's at or slightly above. They know that a lot of students will (usually) do better in their final exams, and offers will depend on other factors too. He could go for one 'lower' one if he's a cautious type, but only if he'd be genuinely happy with the place and course and is desperate to definitely go to university next year.
Don't worry, there are plenty of decent universities for which As & Bs or all Bs are fine for e.g. Chemistry, Mathematics, Chemical Engineering, Computer Science. Some students will do better in the long run in those universities than the absolute "top" ones and sometimes the teaching is better too. It's no impediment to a great experience, great career, research funding etc. of itself.
If he gets better grades than those which his eventual offer was based on, he can probably change universities through the Adjustment process which is concurrent with Clearing and usually has quite a lot of places in science and maths subjects (but not medicine, dentistry or veterinary medicine). This is particularly true if the achieved grades are AAA(A) to AAB(B) At a pinch, he can exit the process, take a year out, and reapply for an unconditional offer for the following year.
He could also seek advice from his preferred university course(s) by finding out who the undergraduate admissions tutor is and talking to them (via email or on the phone). This can take a bit of tenacity - ring the department rather than going via Admissions.
(I've worked on Clearing in a university.)