There are many tricks that let you compose a Gmail message in a new window: you can press "Shift" while clicking the "Compose" button, use the "Shift+c" shortcut or click the "pop-out" icon if you've already started to compose a message.
It's no secret. When engineers built Google+, they constructed an SEO juggernaut to dominate search results above all other social platforms. Although Facebook and Twitter are essential to marketing efforts, both restrict Google from accessing much of their data. This limits their SEO effectiveness.