I'm making a guess here When offline you don't have access to the internet, you can't login without internet as the data on whether its correct or not is on the cloud as it cant be stored on a single device. In that account there is all the data and personnalization which is not stored on the account but on your device. But things like skins are stored on the cloud because if you were to login to a server or online world with a skin and only have it on your device nobody else would see that skin. Just a hunch.
In short the play station doesn't know who you are and cant verify if you are that account without access to he internet so it wouldn't put a skin on an offline player.
I'm making a guess here When offline you don't have access to the internet, you can't login without internet as the data on whether its correct or not is on the cloud as it cant be stored on a single device. In that account there is all the data and personnalization which is not stored on the account but on your device. But things like skins are stored on the cloud because if you were to login to a server or online world with a skin and only have it on your device nobody else would see that skin. Just a hunch.
In short the play station doesn't know who you are and cant verify if you are that account without access to he internet so it wouldn't put a skin on an offline player.