I mean, Lochlan is portrayed as so joyful and free and innocent, both naïve and also didn't do anything wrong. The drugs are absolutely hitting him hard and he's just having a good time. In fact, upon rewatch, there's a scene where Lochlan points to fire dancers(?) and they both look and Lochlan mouths "what is happening," or "how is this happening." He's clearly supposed to be even harder hit than Saxon is. That's why Saxon feels guilty the next day, in large part because he knows he promised to look out for Lochlan and couldn't even stop him from taking drugs that clearly had a huge affect on him. That's why Saxon blames the drugs for the incest, and he ultimately blames himself for the drugs.

Anyway Lochlan did nothing wrong. There's no manipulation, he's not being a little seductress either. He's just surrounded by sight and sounds and his brother and he's having a blast.

Touching Saxon's hair can be seen as a cliché high on Molly trope. But it could also be that Lochlan is already worshipping Saxon and is touching him in a way that feels appropriate for that context. Lochlan just wants to touch him. He's longed to have actual intimacy with Saxon because this guy is a huge source of his validation, affection, love? He's almost like a surrogate father for Lochlan (sound the alarm bells NOW). But things have to be kept a comfortable heterosexual masculine distance. Lochlan is so touched starved he just wants to hug Saxon, bury his face in his shoulder and be held like when he was a small child. All Saxon gives him are bro-y chest and back pats. Physical intimacy between men? Gay!

And don't think Saxon is not also touched starved as fuck. The feeling of Lochlan's gentle hands through his hair has him looking like he's orgasming lmao. And the look he gives back at Lochlan as he giggles at the fireworks is probably the first time he's shown such unfiltered fondness for Lochlan. And it's a crucial moment that lets you as the viewer know, he's not a total sadistic narcissist. He does care about Lochlan, in his own way. But he struggles to show it unironically.

Lochlan struggles to be open with his desires, that is for someone to see him, recognize him, allow him exist beyond what he can do for them. Saxon struggles to be open with his desires, that is for the Lochlussy, just kidding, that is for intimacy that's not coated in macho gay chicken incel nonsense.

You can read both of their desires as fucking each other nasty, or at least that's a manifestation of it. Sure, I don't care, go crazy, it's not real. But since I see the entire point to them existing as being some commentary on gen-z masculinity I don't know... compels me though.

So yeah, Lochlan wasn't trying to give Saxon the cookie, whether you think that's cute or evil. He's not trying to seduce him and he's not testing the waters so he can assault him later. I think the emotional message of the hair touching isn't meant to be sexual, I think it's meant to show that both of them do actually like each other, that they've felt lonely/misunderstood up to this point, and that they're feeling a deeper connection at that moment.