I'd argue that a beginner is probably not well-served by starting with a DA/SA gun.
I would agree with that, particularly if it is understood that what is meant is that they are not as well served as they would be with a gun with a single, consistent operating system. (either SA or DAO)
The DA/SA learning curve is steep, to master both methods. I do own a few guns in that category, one is a Browning BDA 45 (Sig P220) that I bought new in 1980. Despite the two different trigger pulls, I do love the gun. And, I will admit to almost never shooting it DA.
Interestingly, after I had owned the gun for about a decade, and with NO work of any kind done on it, the DA pull weight seemed to be about half what it was when new. No, I never measured it then, and still haven't, I'm talking about the "feel" which could be entirely me, and probably is.
I have, a couple times in my life "discovered" abilities that I didn't think I had. I had a steel plate in my backyard range, that when in my 20s, I struggled mightily to hit shooting a DA revolver DA. If I managed half the cylinder on target, I was having a great day! Then, about the time I turned 30, all of a sudden, I was "ptinking" 6 for 6 slow fire. Where that came from, I never figured out, it just seemed that one day, I couldn't miss, and from that day on, I shot DA much better. I suppose one could say my practice paid off, but to me it seemed like magic, because, I never really practiced shooting DA very much, just something I did once in a while.
Another gun I have in the DA/SA group is my Mauser HSc. Unlike the Sig, it has a safety. And that safety puts it in what I think is the worst group of pistols for a "beginner".
Like a lot of the DA/SA service pistol designs, the ones with a safety or decocker/safety are the most complicated for new shooters to master. And even for some experienced people, as well.
To make the gun "ready" for carry, you put the safety ON to decock, then have to take the safety OFF so you can fire the gun DA at need. Forget to take the safety OFF before carry, and you got nothing when you pull the trigger.
Cooper, who was very ...conservative.. about what he liked and didn't, didn't like safeties on the slide (for one) and the DA/SA concept in general. Writing in his personal style that irritated so many people, he warned about the risks of a decocking safety saying "don't get caught with your dingus down".
While his manner of writing was considered abrasive and condescending by many, to date, I haven't found him to be totally wrong about a number of things.
I have another pistol that falls into the DA/SA group, and its a real oddball, doing it.
The Wildey.
Its a huge gas operated semi auto, mine is a .45 Win Mag. It has a DA/SA trigger set up, and oddly also a heel type magazine catch. It's way out of the "duty gun" class, and I have no idea why Wildey designed it that way.
I suppose the answer would be "because I could"...
Personally, I've never seriously trained shooting a DA/SA semi in DA mode. I guess I would be one of those people who "shot cock" their gun (if I ever needed to do it).
I think its great that people want to train and master the DA/SA, the way I never did. I'm sure that if it comes to a gunfight, they will be better off than I would be. I've managed to avoid a gunfight for 60 years, and I expect to be able to continue to do so for the 20 or so years I MIGHT have left, so I'm not overly concerned.