I see that the eink waveform modes in the mxcfb.h file DO NOT match the new update modes in the eink_panel.c file. Sadly, the new mode was added to the MIDDLE of the table, not the end. Perhaps this is why I can do ioctl() eink updates on everything EXCEPT 5.0.1, and why eips is setting an extra "undefined" bit in the ioctl() call...
EDIT: I see that they added this to magic.h:
#define UNIONFS_SUPER_MAGIC 0xf15f083d
New unionfs support?