I do see what you're saying and can agree. I guess for me, in hindsight, his distant politeness doesn't necessarily equate to him speaking to people he considers Tranquil. Given that the most interaction he's had in the past few centuries are with spirits, I don't know that he would be able to conceal his disdain so well. This is the guy who killed a lieutenant because Felassan was sympathizing with modern elves. Yes, Solas needs to thaw his views by Trespasser if we're going to have a chance to convince him to stop his plans in DA4, but I never had the impression that he had any dislike for his surroundings. If anything, his dialogue with Varric seems like he's trying to convince Varric to reexamine traditional dwarven culture and try to reinvigorate it. He doesn't push too hard and it's more idle chatter than a heated debate, but his stance is "why don't you try to fix things?" rather than "things are botched beyond repair, no wonder you're on the surface."
I've thought so too. For a guy who supposedly didn't see modern people as worthy in the beginning, he shows genuine interest in the other companions and what they have to say.
No sign of cold indifference and contempt.
I think that's his natural compassion at play there. And his natural curiosity.
He saw a world of "tranquil" instead of people(which rankles me anyway cus dammit, Solas, Tranquil are still people, but w/e), but that doesn't mean he hated them. In Haven, he only shows disdain for the Dalish, really, when pressed. And that's not b/c they're Not-People, but b/c they're close-minded as far as what he wanted to tell them and likely tried to shoot him when he approached. Its more a personal annoyance at them there than anything else. Even when he talks about this "world of tranquil" he woke up to in Trespasser, I never got the impression he had contempt for the supposed tranquil of this new world. He had pity and he had guilt cus it was his fault. He doesn't blame those in modern Thedas for their "situation", he blames himself.
So you're not going to see contempt b/c there isn't any. You'll see emotional distance. He pities them, but he doesn't want to get attached, basically. He's seen that getting attached to these modern Thedosians can sway loyalties and derail plans, as was the result of Felassan's attachment to Briala.
And then his plans go boom and he *has* to get in close proximity and, while he's very closed off about himself in most ways that are meaningful at first, its both strategic and within his curious nature to understand those he's allying himself with. So he asks them questions, tries to understand their motivations and why they act how they do. I think his aim there was to able to predict how they'll act in a given scenario. It was strategic, at first. But by later banters (most of which have to take place post-Haven), he's giving comfort to Cassandra, playing mental chess with Bull, and exchanging snark with Dorian. He has a natural compassionate streak (its why he fought his slave rebellion in the first place, after all) and despite himself, he's now gotten attached.
As to the specific case with Varric, Solas is indeed asking him to examine dwarven culture. He sees parallels btwn what's happened with his own people and what is currently happening with the dwarves's civilization on the brink of collapse. And he likely remembers what they were back in the day, when they were "whole", according to his mind. I don't understand what the confusion is on why he's asking Varric about that? I think he's seeing someone who should in theory understand the desire to reclaim the past of his people and instead is very focused on the here and now/future. Its a parallels/contrast thing btwn his own attitude and Varric's and he debates that with him, such as in the old fisherman with the fermented fruit juice story he brings up. Their disagreement over the direction Cole should take is another example. Solas and Varric are very similar men in many respects, but they end up at different places philosophically. I think a lot of his banter with Varric is Solas feeling that out and then trying to understand it.