If waiting list it means that you will be able to get that watch since you are "waiting" or "in queue". On the other hand, an interest list means it is not a waiting list and it is not a commitment for them to deliver the watch to you.
I think someone got smart and decided to change the term to use..
The way it really works isn't related to a list or queue at all. Unless it's a rare watch like the diamond studded Day-Date or Daytona, the remaining steel and steel/gold watches are usually available or will come soon.
The branch manager, or sometimes higher up, may have a say whether or not a certain customer is allowed to purchase a particular piece, especially the ones which are going for high premiums on the secondary market. For that they want to know if you're someone who wants the watch or just want to make a quick profit.
Actually, I've tried asking if a friend of mine could get a steel Submariner Date on my account but the manager was polite to decline and advise it's better he try his luck on his own and not using my account for it because it won't be good for everyone if the company finds out the watch was put up for sale.
Personally, I believe availability is getting much better and they will actually sell you something if you are sincere about buying to keep and not only just targeting the regular hot models. So many nice ROLEX models in the line up and if the AD you like is has other brands, you'd be surprised other brands like Zenith, Omega etc also make very nice watches.
In Dec 2022, I walked into a few AD in KL area and almost all would ask me to try on the watches. Of course there was conversation and when they realised I already have a few models, they would ask me to try those I didn't have and ask if I wanted to be on the "interest list". I just replied asking for a contact card and told them I would send him/her a message if I decided I would like to add one to the collection.