Those kinds of radios work partially on "line of sight", but not entirely. You do not have to be in sight of each other to use them, but they do have limitations. The type structure the signal has to pass through was the biggest affect how well they work. Since the ship is primarily steel or other types of metal, the signal gets blocked, deflected, and scattered very easily. This will drop the range and effectiveness of them.
They worked for TLANE30 because she was in the Spa near the top of the ship and therefore there was not much to block or scatter the signal to her hubby's radio on the island.
Also, I very much doubt they would work (I'm NOT SAYING THEY WON'T WORK) from Deck 2 all the way up to Deck 9/10. There is a small chance it'll work, but I would not put my money or faith into them be to 100% reliable (I wouldn't expect them to be 10% reliable on the ship).
DW and I had a set of very expensive and highly recommended radios a few years ago. From 100yards away - pure line of sight, they did not work. We kept walking closer and closer together till we were 20 ft apart when they decided to work. At that point we were close enough to talk without them.