+ AA6YQ comments below
I finally got around to applying to the League so that they would move my 800+ "New LotW QSLs" to the "DXCC Credits Awarded" column. Then using DXKeeper, everything seemed to go smoothly during the Download, Analyze and Autolink processes, or so I thought since now there is a strange problem as described below.
+There is no problem.
+ When you invoke "Sync LoTW QSOs" or "Sync LoTW QSLs", DXKeeper sends the date-and-time shown beneath the button, directing LoTW to report all QSOs accepted or confirmed (respectively) since the that date-and-time. LoTW ignores the time, reporting all QSOs accepted or confirmed since 0Z on the specified date. Thus QSOs accepted or confirmed on the last date a QSO was accepted or confirmed are reported each time you invoked "Sync LoTW QSOs" or "Sync LoTW QSLs". I consider this a defect in LoTW; not everyone agrees.