If the platforms offer reporting on the site, then you can use chrome dev tools to see if they're calling a backend API to pull the reporting data. If they are, then you can try passing the same request headers to the backend API url to see if it'll return the data.
We've had mixed success implementing this for clients. Sometimes the auth the backend APIs use changes and is annoying to update on your request, but other times it isn't a problem. Like Taylor said, be sure to check their terms and conditions first. Lmk if you have any questions on using this method!