It would simply remove default units (in most case), cannot see any good reason for such behavior?
Might work in case default unit is the only one present, but breaks consistency (and it may not be
always obvious for user which unit it is). Comes from original patch from five years ago, rB7d8f0fce.
This will break keyboard-setting of values, e.g. '2m 33.4cm' would become '2 33.4cm',
totally useless and invalid entry!
86aeb7df96