The AWE book is peer reviewed and thus a reasonably reliable source. Your original work here is not. That’s the difference. To minimize spreading misinformation, cite your sources. You have now given a source, so that now we can verify for ourselves if “cosine gain” is actually used in the field or not, what it is, and how big of an effect it has.
None of your posts in the topic allowed us to do that, for that you would need to do the following: