This is our booklet about diet which you might find helpful: http://www.beatingbowelcancer.org/sites/default/files/images/EatingWellV5.0FinalLR.pdf
These sorts of foods are more likely to cause problems and so, as Chools has said, your nurses are erring on the side of caution. If you are really keen to try them, it would probably be better to start cautiously, and chew very well.
Alternatively, you could go for some smooth peanut butter or mushroom soup (not together!) which may be less problematic but still give you the flavour you enjoy.