I can see where Brian is coming from. Most definitely. It's not a jibe. It's perspective.
I don't wholly disagree with Rick, or yourself, either.
Brian is simply saying concentrate on the craft. Don't think about anything else. What's important RIGHT NOW (because it's a long road, and every second counts) is that you focus on learning as much as you can of what it takes. Discovering your voice is a long road. From what I can gather, he's asking you to focus on that. Because right now, what you will be paid in the future isn't important. You have to get there. (With the knowledge already, that there's obviously the potential to make a successful living. We all know that. You don't need to be given ballpoint figures just yet)
I don't believe it a neglection of the business side. It's intrigue, and that shouldn't be dismissed. Yet, as a new Writer, it's an instruction to focus on LEARNING, and getting to the standard that you WILL be paid. It's kind of "Make every second count", "One step at a time" and "Don't count your chickens" mixed into one.
You're not entering the business yet. Learn the business after you've learnt the craft.