This topic came up a few months ago and I shall fly in the face of the learned opinions above and say that you should study in whatever way suits you!
Although I wasn't with BGS, the groundschool I used recommended a similar study timetable. I tried it, couldn't get on with it, found it counter-productive to my own understanding so I switched to doing a subject at a time and did the progress tests in one hit.
I found I was wasting too much in going back to revise something I'd read the previous week, something that was crucial to understanding whereas, if I blitzed the subject in one go, I was doing this less and less.
Perhaps it's my age and my ability to retain useless information!!
With one exception, my pass marks were all in the 90s.
Cheers
Whirls