This was discovered by the sleuths at WABetaInfo, who trawl through beta versions of the app to find evidence of upcoming functionality being tested by WhatsApp, who said the functionality will roll out in a future update.
This patch will add the option for last seen to be viewable by “My Contacts Except…”. If you choose this option, you’ll be able to select specific WhatsApp contacts that you want to block from seeing this status. Discussing the feature in a post online, WABetaInfo said: “Several years ago WhatsApp implemented three privacy settings: Last Seen, Profile Picture, About.
“These settings allow you to decide who can see those data when interacting with you on WhatsApp. To manage these privacy settings, WhatsApp has implemented three options: Everyone, My Contacts, Nobody.