In all your scenarios the likely answer , even with great e2e is that WhatsApp would still know who you messaged and they might have googled the words at some point.
Your agent might have searched for latches after you messaged them. Your friend likely searched for cat litter before he messaged you.
In each of those cases, E2E may still be active but you’re compromised by the human equivalent of the age old analog hole.
coincidentally, Janes unknown message was about topic C. Likely because she too believed it to be applicable to John.
---
Going further...
Maybe topic A was trending in Janes area. Jane's friend Sally got ads for topic A. sally talked to Jane about topic A. Jane searches topic A
A trend emerged where people who searched topic A, very soon afterwards searched topic E.
Jane is very late to hear the news about topic A. She gets shown ads for topic E. Jane thinks advertisers are reading her mind because she was thinking about topic E but didnt talk to anyone about it.
Your agent might have searched for latches after you messaged them. Your friend likely searched for cat litter before he messaged you.
In each of those cases, E2E may still be active but you’re compromised by the human equivalent of the age old analog hole.