>After the boil is over. This is called "dry-hopping". This contributes no bitterness whatsoever
In my experience, heavy dry-hopping contributes noticeable bitterness. If you have access to hops this is easy enough to confirm: get some lightly hopped beer, add a lot of hops (heavily hopped New England style IPAs can use 1oz/gal or more for dry hopping), and let it sit for a few days. After you've strained the hops out you should be able to taste the extra bitterness in the beer. A quick web search found this blog post with some explanation:
In my experience, heavy dry-hopping contributes noticeable bitterness. If you have access to hops this is easy enough to confirm: get some lightly hopped beer, add a lot of hops (heavily hopped New England style IPAs can use 1oz/gal or more for dry hopping), and let it sit for a few days. After you've strained the hops out you should be able to taste the extra bitterness in the beer. A quick web search found this blog post with some explanation:
https://www.beervanablog.com/beervana/2017/4/17/yes-dry-hopp...