A legit company should unsubscribe properly, but I’ve been around from the glory days of buy-and-sell email lists. I always have that dirty feeling like if I unsubscribe, they will just sell my email off to the next spammer in line.
If I find myself receiving newsletters I don’t remember ever joining, I don’t even trust their unsubscribe links or unsub flow.
Funny anecdote: I once worked for a person who treated every unsubscriber as a personal enemy. Like, if you don’t want to hear from me, I never want to do business from you again! Banned! This attitude still permeates businesses, that the act of unsubscribing means the person somehow hates you or has declared war.