Seriously, how is this even on the front page? It seems that people lately are coming up with excuses to call out any app/software/company based on privacy concerns, just so they get some attention.
(And even if it were general default behavior doesn't mean it isn't pretty crappy from a privacy point of view)
Facebook too, will show a user as instantaneously online even if they have chat turned off for you (I think). On the plus side, Facebook recently disabled API access for online/offline status of your friends unless they've consented.
Is this for just the messenger app or the facebook mobile app?
The limitation is in the API only, you can still see the statuses in-app and online, but you would have to resort to a webscraper to get them.
I find it amusing that we are raising 'privacy concerns' now for pretty much anything. How does sharing whether you are keeping your phone in your pocket or in your hands (and telegram active) affect your privacy? Its meaningless data.