Once shared, the PowerApps app will be accessible by all users who have permissions to access the app. However, in order to make the Power BI content visible to those users, the dashboard where the tile comes from needs to be shared with the user on Power BI. This ensures that Power BI sharing permissions are respected when Power BI content is accessed in an app.
Reference:
https://powerapps.microsoft.com/en-us/blog/power-bi-tile-in-powerapps/