Again, they do not "lease" you a device. You do not pay for the security research device, you just demonstrate that you are a legitimate security researcher (e.g. you don't just want a less secure phone because your personal belief about what makes hardware good or bad), and if you are using the device for said research you tell them about issues you find.

The fact that you personally believe the trade off between security and "freedom" favors your definition of freedom doesn't make it inherently wrong that a manufacturer targets people who want a different definition of "freedom" (specifically the freedom you get on iOS where you know that if you're installing something it can't see any of your data from other apps, no existing app can see you've installed it, and if you don't want it you can remove it and know it can't have left anything behind). The fact that there are articles about malware on iOS, and there aren't the same about iOS tells you that there is a difference in outcomes of these models, and it's fairly anti-freedom to say that anyone who disagrees with your preferred trade offs shouldn't have that option.