Do you have any sources for this? (Even anecdotal such as conversations with people in the know)

I recently built myself a good tool that blocks all sponsored, promoted and recommended posts, and it's been incredible. This information if true would be a genuine concern!

Plenty of discussion about this on HN over the last six months

<https://github.com/mdp/linkedin-extension-fingerprinting>

<https://browsergate.eu/>