Thin cotton on our Panama Canal cruise last year on the Coral. Terrycloth on all our other cruises (Mexico & Caribbean). Go figure? Also, even though I have consistantly indicated bathrobes as a preference on the website, I still have to ask/remind our steward when we get to our cabin. Holland America does this better.
I had filled out the on line cruise questionaire before my last Princess cruise, and it was still necessary to ask the room steward for the robe. This was the same for my wife also. Not to sure what they do with all the information. There is also a section on what type of wine and liquor you prefer. That information doesn't affect you personally either. They do not even ask for a brand, just simply type. Seems to be to general, to be of any substance. Perhaps it's to help them stock the bar or gift shop with the right items for sale?
After your imput on the immagration questionaire, you click on "continue" and you will be asked for personal preferences on your upcoming cruise. This whole section is for people who are actually booked, and have a valid booking number.