Summary notes for maths may not be as helpful for Methods compared to other subjects but they are good for revision
100% agree. I never touched a textbook in PE or biology last year (edit: except in the very rare case that AN and connect summaries were both unclear on something), just used AN and Connect summaries. Understanding those summaries basically seemed all that was required. But maths is so application-oriented that you gotta practise all those applications in a textbook and come up with your own way of understanding the general processes.
My suggestion (at least what is working for me) is to do a chapter exercise (eg chapter 6H) and then write your own notes on that, including the theory (formulas and underlying principles - which commercial notes do cover - yet they only do so shallowly), and also examples of the different question types on that topic (e.g. for chapter 1G of the year 8 maths textbook, which covers multiplication, you might include examples of multiplying fractions, multiplying negatives, and the the geometric significance of multiplication: that a rectangle has an area of its width multiplied by its height etc.). This way you’ll be in control rather than relying on someone else’s notes, and you can even note down where you most often make mistakes. For example, you might have made the mistake of -(a)^2 = (-a)^2 = a^2 which is not true. Thus you would personalise your summary to your own needs to understand this little tidbit
I think the effectiveness of commercial notes for only some subjects is that they are written in English (as is biology), rather than in ‘math’ - which you need to manually translate and upload to your brain I guess