My previous post was based on experience with the Gen1. Now that I have a Gen2, I don't have the problem with .ISOs that are too short.
This is just another indication that WD (or whatever company they have making these things for them) doesn't know what the heck their doing. I can imagine that they have discussions like "Well, lets make it work on this device, but not on that device. And on this other device, we'll have completely different features but not all of them. This'll really confuse customers...yeah...let's do that." Even if they're not, the outcome is the same so it doesn't really matter.