Bike porn

You must be very young. Numerous small manufacturers have used that design since the 1990s, and there are still a few today. It has the virtue of almost zero tooling cost, since it can be made by just chopping up tube and rod stock, but other than that it's not very good; peak stress on the saddle rails tends to be high, angular adjustment is minimal and the whole shaft is usually plain guage tubing rather than having the material distributed according to the various stresses.

I have one on the 29er. Works for me.

But...

The upper clamps tend to be widely spaced which reduces fore-aft saddle adjustment.
Plus it clamps the rails under shear, as the clamps arent above the cradle. So it doesnt look like the beast chioce for carbon rails.