The description of "--max-delete=" option in the man page is a bit ambiguous and open to interpretation:
This tells rsync not to delete more than NUM files or directo‐
ries. If that limit is exceeded, a warning is output and rsync
exits with an error code of 25 (new for 3.0.0)."
The above could be easily interpreted to mean that rsync aborts the current operation as soon as "max-delete" is reached. However, according to my tests, that is not the case - rsync only aborts *deleting* files, but continues with updates/transfers to the end. By the way, I think the current behaviour is good and desirable - I just think that the man page could clarify that rsync will only abort the deletions, but continue with the updates/transfers to the end of the current fileset. Otherwise some users might get quite different results from what they expect when using this option.
Thanks for the suggestion -- this was improved a few weeks ago.