In the early days they would quietly take all your contact info on your phone and send emails in your name that made it seem like you were reaching out to those contacts. Something like “(your name) is trying to reach you on LinkedIn”.
Back then, Android didn’t have app permissions like it does now where you have to ask the user explicit permission for access to certain data. It would only show up on the very first app install and only if you’d be looking for that.
I cancelled my account back then and never looked back.