[FAQ] Does rsync 3.2.7 use ctime or mtime for the "quick check" algorithm?

[Semnodime]

The manual for rsync 3.2.7 states:

       Rsync finds files that need to be transferred using a "quick check" algorithm (by default) that looks for files that have changed in size or in last-modified  time.   Any  changes  in  the
       other preserved attributes (as requested by options) are made on the destination file directly when the quick check indicates that the file's data does not need to be updated.

Regarding said last-modified time, does rsync use ctime or mtime?

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According to https://lists.gnu.org/archive/html/coreutils/2010-08/msg00010.html,

POSIX says that [...] ctime must unfakeably track the current time of any action that changes a file's metadata or contents

, so I assume rsync uses it (and I suggest it should, if it does not already).