The 3.1 manual says in the description of --human-readable:
Backward compatibility note: versions of rsync prior to 3.1.0
do not support human-readable level 1, and they default to level
0. Thus, specifying one or two -h options behaves the same in
old and new versions as long as you didn?t specify a --no-h
option prior to one or more -h options.
There are some differences however: with -hh, byte sizes have commas
in 3.1 but not in 3.0.6. Also, the width of the size column produced
by --list-only changes from 11 to 14. These changes might be mentioned
in the changelog.
Another difference is that --stats produces an extra line, the "Number
of created files". This increases by 1 the number of lines produced by
--stats, so might also be mentioned in the changelog because it could
affect scripts.
