Marlin's bed leveling Mesh Validation Pattern ignoring home offset
A Marlin developer confirmed that bed-leveling and probing are now performed entirely in the machine coordinate space.

To clarify further, if one has a non-zero home offset enabled, the following commands refer to different physical locations despite the supplied parameters being the same:

M206  X10  Y10 ;  Set a home offset in X and Y
G30  X100 Y100 ;  Probe (100, 100) in machine space
G0   X100 Y100 ;  Move to (100, 100) in print space, ie. (90, 90) in machine coordinate space


I was able to correctly align the bed-leveling grid by altering header files in the source code. I defined the XY offset using two new macros BED_OFFSET_X and BED_OFFSET_Y in Configuraion.h and altered the following lines in Conditionals_post.h.

#define X_CENTER ((X_BED_SIZE) / 2) + BED_OFFSET_X
#define Y_CENTER ((Y_BED_SIZE) / 2) + BED_OFFSET_Y


The mesh is now physically aligned with the bed and I have not observed any adverse effects.