You're assuming a VERY high level of proficiency for these hypothetical phone thieves.
Especially since the main goal of stealing the phone (assuming they didn't just find it and decide to keep it) is theft of service. They use the phone as much as possible, as expensively as possible until Verizon blacklists it. Then they'll try and unload it. The thief isn't planning on using the device long (if at all, they might be sell it to somebody else for the service), and will generally unload it to a fence to sell.
That said, yes you can turn off the notification message.