If using babystep to adjust the Z probe offset, the axis will move and the mesh will be updated at the same time, causing a doubling of the Z offset over the rest of the print.
To correct for this, the current Z position would need to be modified in the opposite direction, canceling out the additional Z offset added to the mesh. This would be confusing to users, and moreover it would not be accurate without also taking the current Z fade level and current Z height into account.
It might make sense to change the mesh in the case where no babystepping is taking place, but this could be considered an undesirable side-effect of changing the `zprobe_zoffset`.
One way to remedy this would be to return to storing the mesh with `zprobe_zoffset` included, then subtracting `zprobe_zoffset` from the returned Z value. Thus, a babystep moving the Z axis up 1mm would subtract 1 from `zprobe_zoffset` while adding 1 to all mesh Z values.
Without including the `zprobe_zoffset` in the `z_values` there is no safe way to alter the mesh in conjunction with babystepping, although it's fine without it.
This is a non-intuitive change. @oldmcg says in this post https://github.com/MarlinFirmware/Marlin/issues/7572#issuecomment-340641207 that using DELTA_PRINTABLE_RADIUS is better than DELTA_PROBABLE_RADIUS for setting the probe limits. This is because the automatic probe code checks all locations for being reachable by the probe prior to doing the probe.
Scott Lahteine