Android and iOS preferences and unique identifier

I am planning on storing a unique identifier after a user logs in for the first time on an Android and Apple app. This will make sure that the user can only access data from one device if they try to login through another device as I will flag then as having access. I will save this unique identifier in the devices preferences and use it for requests to get this private data.

With that being said I know the preferences can be deleted or removed. This piece of data isnt needed long term and in emergencies we can reset the users account back as if they never got access yet like for a factory reset or deleted app.

My question is, are there any issues with this? These arent developers so somehow getting access to the user preferences to find that unique identifier and using it elsewhere shouldnt be an issue.