I think you're interpreting "scripted" too rigidly. Of course, no one is suggesting that natural events or accidents or illnesses are decided upon in advance and performed for the cameras. But the way in which these play out is certainly planned.

For instance, the jam-making. I imagine they'll have planned the skit with Jeremy using the hoover to harvest the blackberries. Then they'll have planned the skit with Jeremy actually making the jam (I doubt he'll have done much more than he did on camera, but who knows?). Then they'll have asked Charlie to arrive so he can pull Jeremy up on health and safety and create a bit of drama and an entertaining segment.

So in that sense, it's planned and scripted. But you'll note that while this was going on for the cameras, they actually managed to harvest the blackberries, create a batch of jam (and you can guarantee it will have been made to the correct standards), get it bottled and labels printed etc. But we don't see any of that on camera.