I'd also find it quite useful to have a "filter by date" feature, not just "filter by name". If I have a big sync job and *know* that the only changes are quite recent (e.g. in the last day) then I could run the sync job really quickly by telling WinSCP to ignore any files older than a day -- I'm not interested in WindSCP spending hours checking on the sync status of older files because I *know* they do not need uploading.
Sorry I do not understand how this can quicken the synchronization. WinSCP would still need to compare the time of the file, not against time of the target file, but against the filter time. This would take the same time.