> it enables security minded people like myself to root the device
Actually, having kernel sources doesn't enable you anything except for, possibly (but not certainly), building (but not installing) your own kernel.
You're able to install customized kernel and/or recovery on most Samsung phones, but that's completely unrelated to any FLOSS source code releases. Actually, this is usually done using proprietary tool (ODIN) communicating with proprietary hardware and firmware. They're just generous to allow you to do so (but they tick a flag stating your firmware is unofficial, and recently they started to blow a fuse to prevent unticking)
> it enables security minded people like myself to root the device
Actually, having kernel sources doesn't enable you anything except for, possibly (but not certainly), building (but not installing) your own kernel.
You're able to install customized kernel and/or recovery on most Samsung phones, but that's completely unrelated to any FLOSS source code releases. Actually, this is usually done using proprietary tool (ODIN) communicating with proprietary hardware and firmware. They're just generous to allow you to do so (but they tick a flag stating your firmware is unofficial, and recently they started to blow a fuse to prevent unticking)