In amongst your head messing, you two, there is an interesting point.
As an adult learner, having at one time been a professional management trainer, I know that in situations like learning to play an instrument, I have a need to understand the underlying theory of things and think about them so that I can put them into practice. My teacher recognised this too and while I was learning to play, she got me to do Grade 5 theory before the playing exams. I'm very glad I did because it suited my learning style. It does depend on context though as sometimes I will abandon my theorist/reflector style and go into flat pack building mode of trying to put something together first and looking at the instructions afterwards (usually when something's gone wrong). Other people will be naturally different and will want to learn to play first and only get to the theory later, if they need to. Exactly as Trimmy says.
There is nothing wrong with either approach. However, to learn fully, you need to do all of the processes - whether you start with the activist/pragmatist process (dive in first and learn how it works later) or the theorist/reflector style (understand why and then do it). I'm paraphrasing, but I hope the point is clear. If anyone wants to know more about this (theory!), have look on line at Honey and Mumford's Learning Styles.
BTW, Grade 5 goes up to six sharps and flats, basic voicing, intervals, chords and cadences and some elementary composition. .