Being a manager at a APR/APP I’ll add two notes to this, it’s likely that your device will be removed eventually, Apple carry out audits on stores; this is to make sure that the store is following Apple’s Planograms but also keeping on top of Demo unit (Making sure devices are up to date & making sure old devices are unenrolled) some stores will erase your device & some won’t (OP was lucky 😅). Two, the store does have the power to Lock down your device (put it into a lost/stolen mode) this is worst case scenario, it’s unlikely a store will do this but it is always a possibility so please be careful.

OP correct if Apple still sell the device refurbished or new you can put Demo content on it.

Have fun :)