The “name” of these objects in Viljandi corresponds to the following source:
https://www.puhkaeestis.ee/et/maasikad-viljandis

If you know a better name for it, feel free to change it!

In my opinion, the “relation” makes sense because the objects are related to each other and are therefore easier to find in the city of Viljandi, which is the purpose of a map (OSM). Please refer:
https://wiki.openstreetmap.org/wiki/Relation:site

The data tag Site=stop_area is of course wrong, I'll correct it. Thank you