[Unlimited Data] Did you know?

Did you know that there is basically no more alternate upgrade for unlimited data users? I called into VZW to buy a new device on one of my three lines. My line has the unlimited data, my others do not. I was told that I would lose my unlimited data if I bought a device not at retail price. Of course I said "I know that on my line, but i want to on another line." i was then shocked to hear that VZW has a system where it can see when a device was purchased , if from them, and how it was purchased. If the system sees that a device was purchased on a 2 year or device payment plan, and then transferred to another line, that line will lose unlimited data without notice. Again, this surprised the heck out of me. Seems really shady. I called in a second time and it was confirmed to me again. What are YOUR thoughts on this? Even if you are not on an unlimited data, what are your thoughts from a customer perspective? I do not know by the way if this also applies to data promotions back in the day like my mom has. Personally the lollipop update kinda screwed my phone, so i was going to go S6 Edge+. Thanks guys.