For some reason, Ford decided to use Security Torx to hold together their hybrid battery packs. Couldn’t tell you why that was better then regular Torx.

I’d guess that was some sort of safety standard designed to protect vehicle owners from themselves.

As Torx gets more and more common, it’s presence is less and less likely to be a serious hurdle, so the security screws are a simple way for them to sort of say to the owner “don’t mess with the stuff below this”. If they want to, they still can, but it’s a specific effort at that point…so Ford can say they’ve implemented a safety measure. Might even be some sort of government standard too, where using a less common fastener style brings them into compliance without needing some sort of even less accessible design, like a sealed off system.