Judging from his volume, and breath of work I think Ken Arthur looks like he could be called a professional journalist. I thought his article was ok given Miller's injury history. But you're right in that we can equate Miller's year/injury with Wagner's year because we don't know if Miller would have been injured playing for the Rams.
OTOH, "professional" journalists are really bad journalists, depending on how you set your bar. I've had a family member who worked, as a paid professional journalist for a large newspaper, and I got to learn about that industry first hand. Back then they were a pretty good lot with above average writing skills and they took time to investigate their work. Now, LOL, most professional journalists, are teenage girl gossips.
This industry now needs to get website clicks, or hits, or shares, etc., in order to make money. Consequently, the more outlandish and loud one can be, the better. Who needs truth and facts? Just twist it and make a few provocative statements and predictions.
I would tell you how I really feel about "professional journalists," (isn't that really an oxymoron?), but that would be off topic. I'm sure a few still exist but they are a dying breed and almost extinct in America.