Part of an event called Sternfahrt where cyclists protest for policy changes by taking over the city on 20 routes covering 2000 km of public roads.
some infos in german: https://berlin.adfc.de/pressemitteilung/adfc-sternfahrt-medienkit
translation to english: https://berlin-adfc-de.translate.goog/pressemitteilung/adfc-sternfahrt-medienkit?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp
You assume people are driving safely - in my experience, during rush-hour at 90-100kph (Stockholm) someone will file in ahead of you if you leave more than 2 car lengths of space.
Is it safe? No.
Is it reality? Yes.
Furthermore, this is an estimate of a feasible max throughput that may have occurred.