Actually, it would be more like your tv requiring a power cord made by the tv manufacturer. Or a laptop requiring you to use a power cord made by the laptop manufacturer. Neither of those things are so crazy, and no one complains about them, so why complain about this? And its not like they're saying other cables definitely don't work, they're just saying they will only support the moto/verizon ones. If other ones don't work, its not their problem. Same as with power cords for pretty much any device.
Actually it is similar, but your premise is off. I use a Rocket Fish power cable from BB on my Dell laptop. What does USB stand for? Isn't it universal serial buss. I.E. one standard that works the same regardless of manufacturer. I see enough posts that this is must be an issue on some Bionics, but not mine. My monoprice USB's and HDMI's work just peachy