If the splits are done before the hive decides it wants to swarm it can help. It is common here in FL that before the orange flow or even during, splits are taken. The young bees won't be foraging anyway since the orange bloom is so short. The hard part is predicting the right timing. If you take splits too early and the bloom is a little late then you may be taking foragers but you may also be reducing the need to swarm.
Also, you may be able to split after you see swarm cells. As Brian said, you must take the current queen with a split and it may trick them into thinking they have already swarmed.