Confusion regarding Iphone 5s models and their network carriers.

Why is that the tech guys in apple store always recommend to consumers, who plan to use their iphone overseas, to buy the GSM model instead the CDMA model? Eventhough we know, from a tech savy perspective, that CDMA model can work overseas just like the GSM model because THE CDMA MODEL COVERS THE GSM MODEL'S networks. Don't the tech guys at apple store CARE for the consumers WHAT IF THIS CONSUMER GOES BACK TO UNITED STATES and plan to use CDMA network (Verizon for instance)? The consumers who has GSM model cant have option to subscribe to Verizon.

The same thing can be said to ipads with cellular. Tech guys from apple store tell this.

The reason why Im writing this is there are things that comes out from tech guys' mouth in apple store that dont really match to what the hardware specs has and these uninform specs could cause more money to naive consumers.

Reference:

Model A1533 (GSM)*: UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 2, 3, 4, 5, 8, 13, 17, 19, 20, 25)

Model A1533 (CDMA)*: CDMA EV-DO Rev. A and Rev. B (800, 1700/2100, 1900, 2100 MHz); UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 2, 3, 4, 5, 8, 13, 17, 19, 20, 25)