I thoroughly and repeatedly deleted all stock-related information from my Google account: all portfolios removed, all search history erased, all past Google Now topics suppressed, past emails deleted, Google chat conversations removed. Just everything (and I know really well how to control data on a Google account, I was once a Google fanboy and explored every little feature I could get my hand on, so customizing my Google account/products settings is something I'm quite good at).
Guess what? Going to their new google.com/finance brought all the stocks I've once added to Google Finance and removed. More than a dozen of stock tickers were automatically added to my account, and listed as "following".
It's impossible for me to completely delete my Google account because of some work-related obligations, but Google just proved that it will NEVER allow you to get forgotten.
We're forced to feed a beast we can no longer escape.
PS: the only Google things I occasionally use now are Gmail & Google Contacts (planning to switch to ProtonMail, but waiting for a contact syncing service on Android) and search (when Qwant isn't good enough).