Not really true, but is true that it’s highly random and takes a large sample in my experience to actually find someone.
In my experience, all the event types mentioned are largely attended by single people looking for dates. Even the language exchange groups, which have a highly specific and functional intent, tend to be single oriented.
On the flipside, if platform attempted to enforce maintaining 50/50 balance of user base that’s single or not single and explicit forbids users mentioning dating unless they are above a predefined “friend score” — it would remove a lot of people that are not interested in relationship attributes.
