I do not recall seeing my preferred name anywhere.
They called out my coffee orders with my actual name, until I started asking the IC lady to write my preferred name on the receipt. She was there every morning, so she remembered. They didn't write the names on the cups like they do on RCI ships.
Same with the MDR hostess - she addressed me by my actual name every evening, but she really liked my name, so it's ok. We have a somewhat different issue with our names - they are foreign and hard to say, so we both have much easier Anglicized nicknames which we use in every day life. So, if the crew member is from our countries of origin and can actually pronounce our names - great, but not many can.
So, I think that the crew rarely needs to use the names in the system, and if it is more or less repetitive, like the International cafe or the same MDR hostess situation - it's easy enough to ask/tell them to use your preferred name and they should oblige, unless they forget. Which they try very hard not to.
However, I agree, it would be great if the system worked properly and actually displayed your preferred name to begin with.