Hi @Bastien_Siebman,
I recalled this was just answered the other day:
I feel based on experienced users not noticing this, and general UX principles, that this switch does not belong with the page to create a particular status update and should be moved to the right Update sidebar of the Overview page where it would be more expected. @Emily_Roman, maybe move this to #productfeedback so it can be voted on?
Thanks,
Larry