They're speculating that you can do this using size of the full connection - there's truth to that, but under HTTPS padding will occur causing a round up to the

They're speculating that you can do this using size of the full connection - there's truth to that, but under HTTPS padding will occur causing a round up to the block size of the cipher - meaning that there's a higher chance of overlap in package sizes. It might actually become quite difficult to do such analysis, especially if multiple requests were made for packages at once in a connection that's kept open. You won't get direct file sizes either, you'd have to perform analysis for overhead and such - in any case it's significantly less trivial than an HTTP request logger.