I set a flag in this option, but it does not work as written. This item can be purchased multiple times by the same user, and the user can purchase items of the same type. Please explain that this does not work as intended, or do I misunderstand this option?
Below is a copy of the settings screens of two different items of the same type.


The user purchased both items and there were no obstacles to doing so.

Below is a copy of the settings screens of two different items of the same type.


The user purchased both items and there were no obstacles to doing so.
