The overall rating reflects the current state of the app. It accounts for all app reviews but prioritizes the most recent ones.
Applied for a demo, installed it but it did not work for me. In particular when wholesale customers were logged in. So I mailed the developer to see if there were known issues with wholesale apps. The reply was very rude and basicly said the app was perfect so it could not be. No effort at all into searching what it could be. It might be a good app if it works, but not paying for a customer service like that.