No, it isn't because it limits the damage to devices purchased from a source you can avoid. That you would want to avoid anyway. This device has complete acces

No, it isn't because it limits the damage to devices purchased from a source you can avoid. That you would want to avoid anyway. This device has complete access to your Google account, probably your photos, emails, maybe even credit cards. Smartphone has become such an important piece of personal computing that you want to buy one straight from the manufacturer or their authorized dealer and, since you're on HN, preferably with unlockable bootloader.