There are several factors operating here. First let us think about the pump without a SWG. Turnovers are just a rule of thumb guide to how much the pump should be run. During the summer, one turnover a day is usually enough, but some pools need more and some pools are fine with less. You can figure out a good pump run time by experimenting with different run times and seeing how they affect the water clarity. During the winter you can get away with much less pump run time than you have in the summer. The colder the water gets, the less circulation you need to keep it clean.
Now add in the SWG and things change a little in some situations. The amount of chlorine produced by the SWG depends primarily on the combination of the percentage setting on the SWG and the pump run time. Within some range, you can trade off these two factors to get the same amount of chlorine produced. For example a SWG running at 25% for 4 hours will produce the same amount of chlorine as a SWG running at 100% for 1 hour. Normally you figure out what pump run time you need to keep the water properly filtered and then adjust the SWG percentage to get the amount of chlorine you need.
Sometimes, the optimal pump run time turns out to be shorter than the amount of time it takes the SWG to produce the amount of chlorine you need, even when the SWG is set to 100%. In these situations, you need to run the pump longer to get enough chlorine into the water. This most commonly happens when you have a relatively large pump and a relatively small SWG. In practice what happens is that you get to a point where you need to turn the SWG percentage up above 100% and you can't, so instead you increase the pump run time.
Oh, one more thing. In the winter you need less chlorine, as well as less filtering. In most cases, you can lower the pump run time as the water gets colder and lower the SWG percentage at the same time and still get enough chlorine into the water.