I think the dxii charger will charge previous batteries ie Dx Div etc but you need the DXii charger to charge the DXii batteries. There's a little lug on the RHS of the E19 batt that I believe? stops it being used in the earlier one series chargers.
I have a 1DXii and a 1Div, no experience of the 1DX. I think this is the right way around. I also believe the earlier batteris work in the DXii, but they won't run the later body at "full tilt" so to speak. The DX ii is backwards compatable but the battery charger I don't think is, you need the LC E19 chager to charge the LP -E19 battery , I guess being more powerful there's a different charge cycle at play to charge the E19, but half of me wonders if there is a ruse to make me buy a pretty expensive charger
Fugi you need to speak to Canon Bob, LOL.
.................I might be wrong he wont be
Certainly I can put a 1div battery in the DXii charger. I've just physically done it to check myself but I can't do it the other way around, I just haven't the info one the 1DX, is it using an E4 or E19 batt?
take care
stu