Based on my experience with the last cars I've owned, that sounds like total tosh to me. Even a new Golf I bought in 1999 had facility to turn off the interior alarm.Unfortunately, when customers require to turn the internal alarm off in case they leave their dogs in the vehicle we do have to warn customers it does turn off the alarm system for the entire vehicle."
Leading up to taking delivery of my Tucson next week, in an effort familiarise with certain aspects of the car, I have contacted Hyundai via the chat line and then been passed on to customer service (when I've pushed them) and finally to their technical dept.
I have thus far been totally underwhelmed with their responses and have not had a decisive answer yet. Chocolate teapot springs to mind !!
In your place I would definitely seek the advice of the chief tech in your dealership and others if need be. Also, try and find a salesperson who's running a Tucson as a demo as they might have your answer.