Hi All, find below Apple's reply to WhatsApp bug
"Thank you for your email. Apple relies on each application developer to properly implement the necessary components into their applications that allow VoiceOver to work correctly. We recommend that you contact the app developer directly to provide them feedback on the features you are finding do not work. Customer feedback directly to the developer helps them to improve performance and compatibility."
So looks as if Apple is throwing ball in WhatsApp's court. Hence, everyone facing the issue, please report. After all, numbers do matter.