You are wrong, or I am very lucky. Your example was correct, assuming those customers bought used phones that were PREVIOUSLY purchased from ATT. If you bought the phone new, unlocked, paid retail for it, but did NOT buy it from ATT.. Then they did not seem to care to force you into a smartphone data plan. That had been my experience for the last 4 years or so with multiple phones.
Perhaps it is because I also ran custom ROMS and removed all the useless ATT crap.
Either way I am now using a branded HTC Inspire so am "screwed" into a rip off capped data plan for the next two years. Thank goodness for WiFi!