Not sure that is quite true, at least in 5.24. P703 (#9703) is the enable/disable flag as used in the wizard and scripts. P753 (#9753) is the configured value for spoil board dig in.
M6 macro will set and enable the work envelope using G22 if the configured value in #9753 is greater than zero, otherwise disable it using G23:
If #9753 GT 0 THEN G22 K[#10000 + [#9753 * -1]] ELSE G23 ;If we have spoilboard anti dig in enabled set work envelope for z axis, else do nothing.
M3 macro will issue G22 if #9703 is set to the value one, but will not disable it using G23 if #9703 is equal to zero
IF #9703 EQ 1 THEN G22 K[#10000 - ABS[#9753]] ELSE ;will set the Z work envelope to the current tool length + the spoilboard dig in if the user has this turned on
Therefore, seems the only way to truly disable the work envelope enforcement is to have spoil board dig in turned off AND have the value configured to zero.