I note the link that you refer to. There is a difference between "getting the permission of the UKBA" (which clearly he does not have to do) and "informing the UKBA".
If you refer to the same section you will see the following:-
"If your new course will end before your permission to stay expires, you must tell us by sending an email message [email protected]
This means that he does not require permission, but he is obligated to update by email. I accept that it is not very clearly drafted, but it is the case. The breach is a minor breach though particulaly as the lack of clarity could be argued in your brother's favour.
There is a difference in respect of "leading to". The course that he switch to last year you referred to as ".. at level 5", so I took this to mean that it lead to level 5. If it was at level 5 and led to level 6 then you should be okay.
As to academic regression, if it is the case that the course is NQF5 leading to NQF7 then I accept that ultimately the final qualification is the same. Coupled with the fact that he has not been able to pass his exams I would say that it is not academic progression as such, perhaps not regression (though I would expect the UKBA to view it as regression) but nevetheless the requirement is to show progression and I find it hard to see how not passing exams and switching to a course presently at a lower NQF level (albeit leading to the same NQF ultimately) would be seen as academic progression by the UKBA.
I practice immigration law for a living, there is no science behind it and the above is from my experience dealing with he UKBA.
He has a chance but I would not be confident. Worth making the application but being prepared for a fight on appeal I would suggest.
Trust this clarifies, please click accept otherwise I do not get rewarded at all for the time I have taken to answer your question. I will answer your follow up questions.