I made this recipe this morning and it was fantastic. I had read this post before so I was cautious. I made sure I used 500g of banana and I added 30mls of water as per the carrot soup recipe. I intended on using it for a pancake topping so I was not going to puree the mixture at the end. I cooked it for 20mins and was happy with the result. If was pureeing the mixture I could have easily cooked for another 8 minutes without worrying about drying it out. I am new to pressure cooking, but it seems to be important to have the gas burning just high enough to maintain pressure, I had more success using the biggest burner on the lowest setting rather than a smaller one on a higher setting.
The end result was beautiful, but a little syrupy, I will try again without the water. The colour of my cooked banana was darker than the colour indicated in the book.