Yeah those two plane ones are still inferior to a free weight exercise, you are not stabilizing the weight anywhere near as much as you do on a free weight squat etc.
As far as the linked item goes, it looks really annoying to use, I would not want to do weighted dips that close to the ground and be forced to kick my legs so far behind me, plus on a full range of motion the plates on the weight belt will hit the ground for sure, in the pic the guys got a small 25lbs plate or something and is not even close to full ROM and it's near the ground.
Can't believe a $5k machine doesn't have a real pull-up bar or come with a dip attachment. For $5k you could've bought a nice power rack w/ pull-up bar, lots of nice bumper plates, oly bar, dip bars, bench, rings etc etc. Return the smith if you can.