Do all iPhones really delete themselves after 10 failed passcode attempts?
No it isn't.  There is an option that has to be set on iPhones and if you set that option, it makes you wait longer times in between repeated attempts. If your phone gets stolen the thief can only  try 10 times and on 11th attempt the phone will erase. But again the owner has to set that option for it to take effect. Yes Apple allows the owner of the phone to set that up if they want to. And you can turn it off when you choose. The default setting is off.