The options -preserver-atime restores the last accessed date of all the files specified on the source.
When we scan a SMB share, the access time is modified on the files (if the storage system is configured to modify atime on read), because XCP is reading the files one by one. XCP never changes the atime. XCP just reads the file, which triggers an update on atime. Use the -preserve-atime option to reset the atime to the original value before XCP read the file.