This is completely correct. By having knowledge of all layers, ZFS is able to easily offer features that other systems don't.
One of my favourites what happens when you set a filesystem to keep two copies of a file. Instead of placing the second copy on a random device determined by the RAID layer, it will attempt to ensure that all blocks from one device are placed on the adjacent device.
The advantage of that is non-obvious at first glance, but what it means is this: When two devices in the JBOD fail, instead of corrupting all the files when *any* two devices fail, it means you will only have corruption when two *adjacent* drives fail.
In a 5-device JBOD, that means the chance of corruption when the second device fails drops from ~100% to 25%.