Do the SEOers in professional companies do grey/black hat stuff?

Just a random question popped in my head. Do the SEOers in professional companies do grey/black hat stuff? By professional company, I simply mean a company with office space and employees hiring full time SEOers. I wonder if they only do white hat stuff or low key do grey/black hat stuff too which no one would talk about loudly.

They stay under the radar. Agencies work with clients who have budgets.

They do forum links, sponsored content, guest posts, tiered link building and sometimes do PBNs but this varies.

They have their own domains with really clean link history. They use one domain for many clients. These are not classic black hat PBNs.

Generally if PBN can be avoided, they will avoid that. They do redirects often.