I’m not familiar with how Netflix’s ad tier works and am almost afraid to ask, but could someone ELI5?

If a company wanted to push an ad on Netflix, wouldn’t it be up to them to decide whether to use AI make the thing? Or is this sort of the equivalent of a small business sending a script to the local radio station to have the DJ read it (i.e. rather than producing their own ad), except they add some AI-generated visuals?