Spock probably thinks he’s being SO straightforward when he initially starts flirting with jim. He’s like…. “prolonged eye contact? Check. Stood 72.4% closer to him on the bridge today? Check. Told Jim I found his illogic fascinating? Double check. Soon we will progress to lingering sleeve touches and conversations about our mutual interests. I estimate I’ll be able to propose marriage within the next decade” and poor Jim’s just like “bones I might be wrong here but I think Spock might actually like hanging out with me. It’s just a vibe but it’s definitely there. Do you think we’re friends yet? Do you think he likes me? I just don’t know”
Honestly, I like this head cannon so much better than the more popular one that has Spock chickening out at the last second because he suddenly decided he’s afraid of his feelings. Like maybe the whole reason Spock went to purge his emotions was because he figured he wasn’t getting anywhere with Jim despite doing the Vulcan equivalent of throwing himself at him. Like he figured that he wasn’t going to continue pursue a lost cause but he couldn’t imagine living a life feeling unrequited love on the sidelines, so he’d rather feel nothing. Meanwhile Jim is thinking that they’re finally getting to the point where he might possibly make his intentions a little more obvious and see how it goes, but is just flabbergasted when Spock suddenly leaves after the end of the mission without explanation.