As I wrote, the better schools can integrate relevant theoretical knowledge with the stage of flying training being undertaken at the time - if they so wish.
But if people wish to do the groundschool and exams first, before they have any real idea about what the topics really mean, that's up to them. That became increasingly popular amongst those who wanted to do some intensive PPL course in the US after having first passing their exams in the UK and I'm not convinced that this was a satisfactory way of learning to fly.
Quite why anyone would pay £999 for an intensive 5 day course to take their PPL exams, when they could take them at their leisure during structured PPL training, with a far better understanding of the content, is a bit of a mystery to me.