You can't override section access because it is actually reducing the data in the app for that user. It isn't a matter of hiding it. It in theory does not exist for them.
I can think of two ways of getting around this:
1. Remove Section Access and leverage user limitations in the set analysis normally, then leave items like the Top 15 without it. (Not suggested, because they will be able to leverage filters to see others data and create their own charts, etc..)
2. Include an aggregated table or field that isn't restricted in Section Access. This would be aggregated in the script and the separate/new fields would be used for the Top 15 Sales chart.