Here's my take as a relatively new diver (57 dives): When you start out, there is alot of stuff that you need work on, buddy skills, alot of gear that you need to become familiar with - especially if you are diving rental gear where the set-up changes, etc. Especially if you are diving with another new diver - then you also have to worry about their gear, their skills, etc. etc. etc. I agree, there is no brightline rule regarding
when you should bring a camera in. It is more a function of when are you a good enough diver to
add a new piece of gear, a new thing to handle, learn, etc.
Quite honestly, I wasn't ready for that until about Dive #25. Primarily because I did my OW cert, then had a 2 year hiatus, and then got back into diving on holiday and was only diving warm, not in my local cold water. So at dive #20 I was still very new. We did a liveaboard around Dive #12 to the Channel Islands where I had a lot of opportunity to work on my skills. It was not until after that point that I felt more comfortable with my diving that I decided to start bringing a camera. And only then would I bring it on calm days at sites that I was familiar with. To this day, if a dive looks sporting/challenging or if I am a really unfamiliar dive site which will require more skill, I will leave the camera on shore. I have left my camera behind on several dives b/c of these things.
Like NWGratefulDiver's article and post stated, it is REALLY important to realize that diving and being a good diver is the most important thing. Photography should really wait until you have good skills, especially buddy and buoyancy skills. Until you are comfortable with those two essentials, you should wait. Plus, it gives you something to look forward to doing and helps you power through some of the learning of the less "glamourous" skills.
Best of luck regardless!