I just noticed that the plate does not support split backspace. Without there being explicit mention about different plate options, I guess the answer to split backspace support is "no".
Since this is an IC though, I'd like to ask if it's a possible option. I'm too new to this to know if it's possible to do a universal plate that supports both options. It should be possible to support the option of split backspace with one PCB though.
EDIT: I guess, worst case, open sourcing the plate file, and supporting split backspace on the PCB would allow owners to make their own plates with split backspace support.