Find My Mac already in use (on a bought Mac) - how clear this option?

I bought a used Mac Mini (2018) from a (used Mac reseller), and today I've noticed that the previous owner is still signed in to Find My Mac (but it is me who is signed in to this Mac's iCloud). Looking at: Preferences -> Internet Accounts -> iCloud -> Find my Mac I see: Find my Mac already in use (as on the attached screenshot). When I click on that option it displays the previous owner appleid email and asks me for his password (which obviously I don't and I won't have). While doing the clean reinstall I went through the NVRAM clear procedure, so I assume it was cleared then, or this is a variables that cannot be cleared this way. I found this article, although it is old, describing how to reset the appropriate NVRAM variables: https://tidbits.com/2016/07/22/disable-find-my-mac-by-resetting-nvram/ The solution from the article is to do: nvram -d fmm-computer-name nvram -d fmm-mobileme-token-FMM I didn't do that yet, because: 1 - it should've been cleared already so it probably got recreated based on my Mac's serial, 2 - I read in some places that this doesn't work anymore, 3 - I'm not sure if that won't block or break current configuration of my Mac. When I do: nvram -p | grep fmm it returns 3 vars:

fmm-mobileme-token-FMM
fmm-mobileme-token-FMM-BridgeHasAccount
fmm-computer-name

The first one contains the email and some data of the previous owner like name and email plus some encoded data. My questions: 1. If I want to regain access to Find my Mac then the only option in that case is to try to contact the previous owner and ask him to remove this device from his iCloud? 2. Can this user still block / erase remotely my Mac as long as it is present at his iCloud? Does it change anything that I'm successfully logged in to iCloud on this Mac?