Flow Chart Model Styles can only be applied to connectors between symbols, not to the symbols themselves. So, when you create a Model Style for a Flow Chart, it will show you the symbol(s) that were used in that chart. However, if you see a Flow Chart with triangles and you want to apply those triangles to the current chart, you cannot do it with the Apply button in the Model Styles dialog.
To change the symbol type for a particular Flow chart or separate objects in that Flow Chart you must do the following steps:
(1) Go to the chart level
(2) Select the objects for which you want to apply the symbol
(3) Select Symbol from the Flow Chart Menu
(4) Select the symbol you wish to apply
(5) Click the Apply Button