Welcome the Technical Support section. Help us in assisting you by providing us with a concise and descriptive elaboration of your issues. Be specific and if possible, provide us with a step-by-step instruction in replicating your problem.
I made some test at your site, there is no issue with stream privacy.
only super user and administrator can see all users status, no matter what they privacy.
can you give me the login detail for that user?
if previously that user having privacy as Public, and they made a post. and after that they set privacy as "Friends" only.
the posted stream items will always stay as public. only new stream will having "Friends" privacy.
each stream items will always have they own privacy, as you can see at each stream items, there is privacy icon.