It is triggered by players who explicitly request to have their data removed. This can be done through customer support, and often happens when accounts are removed on the account owners request. Consumer are increasingly aware of this option, as new privacy law rolls out throughout the world.
Up to multiple requests each day for me, and I’m not a large game creator. So, yes.
Data only has to be removed when it contains Personal Identifiable Information (PII for short). This includes any data that can trace back to a player, or contains any player-inputted text or choices (options), or contains progression data that can otherwise be considered personal.
If a game does not save PII, and only saved data to the UserId which is an anonymous key as far as the developer is considered, Roblox is the only party who has to act on these requests. It is safe to save simple data such as currency amount, items owned in inventory, and purchased developer products in your data store as it is not considered PII or is excluded under Right to Erasure requests. This is because the privacy laws these rights are based on, state that businesses (you) do not have to remove these financial records as they must be retained for various purposes (such as tax, customer support, etc).
I myself don’t store any PII in my currently existing games, and am very careful with what I add to my games as a result of these updated privacy laws. As soon as Roblox removes the player, the links between PII and the anonymous UserId are broken. At this point, the data in my datastore is fully anonymous and the only bit of PII saved (the UserId) is no longer considered PII. And thus, if you follow this strategy, you don’t have to act on these requests.
If you do have to act on these requests, such as with your ‘Notebook’ example (which clearly saved player-inputted text), you must act on these requests. This is often done through a command line snippet that removes data of all supplied UserId’s, that are copied from the messages Roblox sends you. Some developers also add an in-game command prompt such as Cmdr to their games to handle these without having to open studio.
Unfortunately, at this time these requests would have to be processed manually. This can be an important reason not to save PII into your Datastores.
Whether this is a bannable offence as far as Roblox is concerned is unknown, as I am not aware of any developer who has been suspended for ignoring Right to Erasure requests. However, you are responsible for complying with privacy law in your own games. Roblox simply informs you that a player has requested their data to be removed.