I hate when people use the word "proof" in this way. This doesn't prove anything, it does however strongly suggest in a perfect network environment that there is something going wrong on SE end when the reconnect happens. You can still get error 2002 at any other point other than the 15min increment if you lose packets or drop connection briefly which is what the OP mentioned multiple times throughout the comment section which you ignored entirely.

This feels like a typical media article misreporting research and spreading misinformation.

Tl:dr - error 2002 occurs if you lose packets at any point during login, AND it can occur server side when attempting to reconnect you every 15 minutes.