Yeah, Id defo be interested in what he had to say about it, esp as he done Grade 4/5 before starting it. (Ive done Grade 1 RGT Theory so far) Id be interested to find what the work pace was like, value for money and did it actually improve his knowledge. Obviously, the end qualification is quite important also but Id like to have his thoughts for sure.
I took Berklee's "Music Theory Specialist" degree course last year, which is their three core theory courses in a row. I think you get a pretty good idea of the syllabus and course materials from the info on their website, and for me it did live up to expectations.
The teaching was basically reading material online with some sound clips along the way. Each course progressed by releasing one of these lessons per week - you'd read through that material and then do the set exercise, which was typically a Finale Notepad document to be filled in. There were a few which were little interactive web exercises. The course's instructor marked your exercises and gave feedback.
I didn't find there was much chatter or peer-to-peer learning among students on my courses, and there wasn't much activity beyond that core stuff mentioned above, which I guess I'd hoped there might be. Not much sense of a class/community. But the instructors' feedback was always helpful and generously given, and they were receptive to any questions, so that was definitely a plus.
I'd certainly say it improved my knowledge. I was coming in with pretty strong music theory on the classical side, but the Berklee take on theory is much more pop/jazz oriented so it really stretched me in that way. I'd guess I spent 1-3 hours on it each week depending on the material, and came away feeling I'd significantly expanded my theory knowledge.
Hope that helps! Happy to answer any specific questions, just shout.