I'm not sure whether this is me not understanding symbols properly or not, however, when I have Synchronise selected and have Power Duplicated a Symbol updating one of the symbols with a new colour only updates the symbols following the selected one.
1) Open the Symbols tab
2) Draw an elipse and fill with a red
3) Click on Create, the Symbol is created in the tab
4) Ctrl+J this symbol and drag to one side
5) Ctrl+J to Power duplicate the symbol the same distance as the second symbol
6) Ctrl+J a few more times
7) Select the fifth (random number but not the first three)
8) Change the colour
Observe:
The later symbols update as does the Symbol in the Symbols tab but the first few do not there is a redraw issue which can be overcome by zooming the workspace.
See screenshots: