This is a good idea. I almost always get caught by this. Last week I had to make Notion account for something, immediately started getting daily spam from them. It's the same everywhere, they think signing up is somehow a license to spam. It has the opposite effect, it destroys any good will towards the company.

Slack is another big offender. Every time you sign up to a new channel you're back on a spam list for some reason. I don't know who is coaching these people, but like notifications, it's a big reason why I often just don't bother signing up for stuff