Gitlab doesn't filter by group/subgroups in projects explore

Gitlab documentation Search through GitLab | GitLab states that you can filter by group in your Projects->Explore tab. (https://service.crazypanda.ru/v/monosnap/2021-04-02-12-25-04-A30VS.png)
But if I try to search by group/subgroup name on my self-hosted instance I recieve empty results.
The same behavior on Gitlab.com. For example Projects · Explore · GitLab but there are groups and subgroups with the name “pythonidae”
Is it bug or I just missing something?