I think the reason why the reports in the video do not show any findings or less findings then expected, is because the agent does not have outbound access. In this case the AWS Inspector only does the Network reachability check. You do not even have to install the agent to have this check done.
From AWS Inpector documentation:
The Amazon Inspector agent initiates nearly all communication with the Amazon Inspector service. This means that the agent must have an outbound network path to a public endpoint so that it can send telemetry data to the endpoint. For example, the agent might be arsenal.
Good call, thanks for posting this!