-> irc.server.com PRIVMSG *status :detach #dstdfgfdg
<- @time=2021-12-23T19:32:05.219Z :eahm!ident@host PART #dstdfgfdg
<- :*status!znc@znc.in PRIVMSG eahm :There was 1 channel matching [#dstdfgfdg]
<- :*status!znc@znc.in PRIVMSG eahm :Detached 1 channel

I see now even the other client has PART but it keeps the channel open after the detach, only the userlist disappears but the chats stay there.

@Epic, no it doesn't and shouldn't close the chan tab if you have "Keep Channels Open" checked.