Nandor's better to Guillermo than I remember from my initial watch. It's still regressive (and it was starting to head that way in 4x10 too, so maybe this just continues from there), he still has times he's thoughtless and dismissive. But he's the one advocating the others listen, and that they do nice things for Guillermo. He's noticed something is wrong just like Laszlo, he just comes to a different conclusion. He listens to an offhand remark from Guillermo that wasn't even directed at him, just to get him a present.

Any shittiness he's engaging in comes from the very idea of Guillermo being a vampire. (The way Nandor brings that up to the others almost feels like he's been floating the idea in his head, which is a whole other thing; I'll see if I'm right with more episodes I guess and we'll take it at face value for now.) And aside from not wanting that to happen because it would change things, maybe lead to Guillermo leaving, etc it's laughable to him right now for the same reasons it would have been laughable to him in season 1 or 2. Guillermo is a little more assertive than in those years, but he's completely returned to the familiar role. He's reacting to Nandor with fear, more than he did even then.

Guillermo's big attitude change came with being a slayer, and now he seems to have forgotten that completely to the point that he doesn't even consider it as one of the reasons the transformation hasn't worked. He wasn't ready, he was in pain, this isn't how he imagined it (insert @cookinguptales's excellent meta on how it's all a big metaphor for virginity loss). And right now he doesn't know what his body is doing, and he's walking around consumed with guilt and imposter syndrome. Becoming a vampire is making him forget other real, important parts of who he is.

I think it's very easy for the vampires to regress - because of time, stagnation, etc - to an earlier point. Guillermo's regression is just as rapid-fire but it's from trauma. His intense desire to not want to talk about it, to wait over two weeks before the camera crew wears him down enough. To try and describe the turning as sexier and more intense and life-changing than it was, only to be jump-scared by Nandor and reminded that what he did was a (fully justified) betrayal. Has he forgotten that if Nandor really did want to kill him, Guillermo's kicked his ass without his now-perfect vision, and has killed dozens of vampires at a time? Or is the thought of hurting Nandor and fracturing that relationship the thing that hurts far worse here?

I'm a little insane about how, while in the process of going behind Nandor's back, while he's right about to get the thing he's ostensibly attached to Nandor for, he's insisting that Nandor will eventually do right by him and really truly cares about him. So much that Derek again asks Guillermo if he's sure about this.

Even more than the love search stuff Nandor dealt with over two seasons, all of this seems tailor-made to address the big unspoken questions of their relationship. What does Guillermo hope to gain as a vampire? How much of that involves his feelings for Nandor? What matters most to Nandor when it's Guillermo vs his own pride, especially if there were a real threat of losing him? Can they actually find their way to eternity together, and what does that look like when they do?

Which is to say, it's absolutely happening this season. And shit's going to get insane on the way.