I believe you may be taking this too literal. Multiple of developers store data by the player’s UserId. I suggest you should look at the announcement for this change in TOS.
It was mentioned there by one of the Developer Relation Staff that its recommended to store data by UserId
ROBLOX usually sends you a message telling you if you need to remove a certain user’s data where you can use the UserId to index into your DataStore to remove his/her data.