This isn't really relevant to the question of Carlos and where his trust really lies.
He and Harry agreed to a plan where Carlos was to suck up to the Merlin-loyalist mainstream, lean in on the letter-of-the-law enforcement, and generally work his way up the "traditional" ladder of trust inside the White Council... all the while keeping his ears and eyes open for discrepancies and oddities that might reveal "Black Council" agents.
Now, we can't tell: is he still doing that?
Carlos is acting that way... years later. Without ever touching base & confirming with Harry that he's still sticking to that plan. And similarly, he's acting like his trust in Harry is slipping, like he thinks Harry is compromised, maybe no longer trustworthy.
But then, according to their original plan, Harry was supposed to act just the opposite, the White Council member getting impatient with WC restrictions, making dubious alliances and even allying with rivals and enemies of the WC. Harry has sure been keeping up his end of things! So of course, "conservative Carlos" has to act like he distrusts Harry.
And we -- the readers -- are stuck wondering if Carlos really has turned against Harry, or if he's just playing his role so well he's fooled Harry, too!
I think the first WC wizard besides Harry himself (and Margaret LaFey) to learn of Thomas' parentage (and being Harry's brother) was when Harry told Ebenezer near the end of PT.
Indeed; I'd argue that this is decent evidence that Carlos is still on Harry's side: Carlos staged that little melodrama -- showdown on the dark road -- to demonstrate his own "I'm with the Merlin" credentials, face-down the "problem" Harry Dresden, and to let Harry in turn demonstrate his "I'm a loose cannon, with dubious alliances and possibly under the influence of Lara Raith" credentials.
By this analysis, Carlos was sending a message to Harry: "look how I set up a confrontation where you had to refuse cooperation, full of over-the-top melodrama, let's ham it up for the undoubted post-confrontation debrief and likely observers-in-the-dark."
You've made a good argument, I'll grant you that. I think it
could be right. I'm not saying I believe it, but I wouldn't rule it out, where I might have before I read this.
I think it might also be
partly true. I think Carlos might be, partly, playing an act with Harry, but at the same time no longer sure about him, either. So his warnings at the confrontation might be both at once.
One thing Carlos said that could be read either way, or both at once, IIRC, was to advise Harry to stop talking before he said something he 'can't overlook', or words to that effect. That implies that he doesn't want to take Harry down...but it might also be a warning that Harry is close enough to the line that he can't rule out it coming to that.
There might be multiple meanings in play all at once in Carlos' actions in that scene.
