Isn't that the first step though?

Deciding, this is who I am, I stand with my fellow humans that suffer under oppression? If you don't first claim that identity, how can you do anything?

Yeah, maybe not the literal label ally, if we want to split hairs, but the path to solidarity begins with identifying as a person that rejects inequality.

You can't just claim the label without backing it by action, but that's anything really.

While actions speak louder than words, gatekeeping the term ally will do us very dirty. The easiest way to turn someone away from a good cause, is focusing on the individual instead of the system and setting high standards.
"How can you be against climate change and still drive that big car?"
"You are against racism? How many black friends do you have?"

Being an ally is about your intention to accept and support queer people around you. A Billion of them will change the world in ways a ten thousand activists never could.