If we look at the way that the pistil develops in the bud we can get an idea why sometimes there are three separate styles each with their own stigma. We find that early in development there are three that start to develop and that a little later they normally fuse together into one. A split stigma indicates some sort of defect or problem occurred during development that caused them to not fuse properly. Sometimes that may mean that the separate styles do not have proper channels within them and sometimes one or more of the separate styles might have a proper channel. However, even if the styles have proper channels there may be other developmental problems in other parts.
Sometimes one or more of the separate styles/pistils might produce good seeds if pollinated but that might be different for each flower with a split pistil and might be different for different cultivars.
In a normal flower there is only one style and one stigma but the stigma normally has three stigmatic lobes. Sometimes a pistil may have a fourth stigmatic lobe (smaller than normal) and sometimes those lobes are not at the top of the pistil but part of the way along the style. So sometimes the pods that develop have more than three chambers even when the flower was not obviously a polytepal with more than three petals and three sepals (or more than six tepals) and possibly more than three stigmatic lobes in the normal location.
If the pistil is split then the abnormal flower could be described as having three pistils and three styles, etc.
