I agree the chances are slim that they are carried into the tank on soft tissue, but chances are not 0%. Also agree, 2 weeks normally enough for the majority of ws to complete life cycle, from what I've seen in my tank, it is around 10 days between outbreaks.Ok, I have not redone my whitespot research the last 3 or 4 years. From when I did my read ups, the WS after dropping off, will crawl around on substrate looking for a place to turn into a solid hard casing.
For me, once the WS encysts, and if on the soft tissue of an anemone, the normal movement, shrinking at night, inflating daytime of the anemone should dislodge it and the cysts would drop to the substrate. I got no proof, just my logical thinking trying to work it out. Other corals with hard skeleton would be able to carry the hosts on the hard portions.
Anyway, after 2 weeks with temperature of around 25 Celcius, the cysts would have hatched by now looking for a host fish that is not there.
I do agree that overly extended QT periods is not good either.