That's of course a lie. Both from practical standpoint (police will invent stuff out of whole cloth if needed with courts rubber-stamping it) and from legal one, too. КоАП РФ [1] article 20.2 6.1, "unsanctioned gatherings leading to interruption of… pedestrian flow… up to 15 days of detention" (do I need to explain that any gathering is in practice an "interruption"?). Moreover, УК РФ 212.1 [2] says that breaking the previous one twice in a half year is punishable by up to 8 years in jail. I'd also like to remind you about the case of Ildar Dadin [3], who got thrown in jail for 3 years for one-person pickets. Sure, he was released when the case got widely publicised, but the laws and court system that did it are still in place.
I reckon you have a very… optimistic and cursory knowledge of Russian laws in that area.
According to [1], you are right and this article is used as you described against targeted political activists.
At the same time, it is not how it is used in general case [2].
Moreover, if you look, for example, at the preceding article (20.1 - disorderly conduct in public places) [3] you must conclude that in Russia people are jailed for 15 days for saying 'fuck you' to somebody in a public place. Which, of course, is not happening because the degree of punishment, while at the judge's discretion, has to be proportional.
I reckon you have a very… optimistic and cursory knowledge of Russian laws in that area.
[1]: https://ru.wikisource.org/wiki/Кодекс_РФ_об_административных...
[2]: https://ru.wikisource.org/wiki/Уголовный_кодекс_Российской_Ф...
[3]: https://en.wikipedia.org/wiki/Ildar_Dadin