My understanding of it is that winterizer does below ground what regular fertilizer does above ground - it makes your roots have a growth spurt and dig deeper. I've always been told to winterize around Labor Day (in Jackson) so that your grass will have about a month of growth left for it to work before going dormant. I've got Bermudagrass, but I think the same thinking applies to all of them.
My experience w/ pre-emerge has been pretty good, putting it down in Feb., but this past year our winter was so warm that I already had weeds going when I put it out, which didn't help. Usually wears off sometime in July or so and crabgrass starts popping up.
But I think you're right - winterizer doesn't have anything to do with weed control, and from what I've heard the winterizers out there that also say they have some kind of weed control built in don't work that well on killing weeds. I usu. just let the cold weather take care of my weeds this time of year.