Hi, I've found a similar table and agree with your changeover assumptions. The table does not seem to be complete. I'm assuming the "Crossed Box" is missing at FL315 and above the 280 kts /.76 column.
I'll investigate your .75 descent changeover FL and your 270 kts climb next chance I get.
I find Airbus is poor at providing information for pilots, it's almost as if they attempted to design the pilot out of the flight deck.
Rgds rudderrudderrat