The mashed banana thing is crazy. If it's just one mashed banana on toast, for instance, then I'd not bother synning it. Mashing three or four, maybe then you're just being silly and not SWing right.
Wrt speed in foods, it depends in how you make your bolognese. mine, I have celery, onion, grated carrot and tinned tomatoes in. I also then fry mushrooms, peppers and courgettes and top my pasta with that then the bolognese. Mainly because my DC wouldn't want the extra veg. If you're adding all that veg to bolognese, then it should be fine.
The reasoning behind the third speed is that you're replacing free foods with speed foods, so you shouldn't be having as much pasta as you're replacing that space in your plate with the speed. If you have a massive plate of pasta and adding speed packed bolognese, then you're not going to lose much weight.
I occasionally will have a salad alongside my bolognese in the same plate, and it does mean I have very little pasta. Still feel full afterwards.