Hm, I tried this:
edit = arcpy.da.Editor(gdb)
edit.startEditing(False, True)
edit.startOperation()
# with arcpy.da.UpdateCursor('swXsectionPoint','Point_Type') as unk_csr:
# for unk_rec in unk_csr:
# unk_rec[0]="UNKNOWN"
# unk_csr.updateRow(unk_rec)
arcpy.CalculateField_management ("swXSectionPoint", "Point_Type", "UNKNOWN")
edit.stopOperation()
edit.stopEditing(True)
And it is still giving me strange results. Tried doing it out of an edit session as well and still no luck. Also, the Update Cursor shown commented out above seems to work. Will put in a support request. Perhaps I need to compress the gdb, or maybe I found a bug.