My favorite thing about this scene is how clearly Fitz is trying to downplay the date, and - maybe this is more headcanon than meta - but I suspect he’s doing it for a specific reason. He knows Jemma so well, better than she knows herself sometimes, and he knows even before getting to the restaurant how touched she would be by his actions. Jemma, her inclination towards understatement and suppression notwithstanding, is something of a romantic, which Fitz knows well (he’s present at both of the season 1 moments above, in addition to having the experience of almost a decade of their best friendship). So her instinct in this scene is to want the whole thing to fit this sort of idealistic image she has of what their date should be like - and in her head, everything fits except for her.
Fitz knows that she’s just barely holding on, and his goal here is not for this to be a perfect first date, but to show Jemma what they have to look forward to. To help her “feel human” again, like she did for him. But he also knows that he’s toeing a delicate line with Jemma’s mental state at the moment, and so he undercuts the romantic aspects of his actions by trying to stop her from pointing them out. He dismisses her attempt to point out the fact that he held a table for six months while he searched for her, and when she doesn’t know how to reciprocate his (arguably intentionally nonchalant) declaration of “what else was I gonna do?” he tells her outright that he’s not expecting anything from her in return. In the best way he knows how, he’s grumping in order to try to make the night about her, and not about his actions.
(Of course, I also think that Fitz genuinely underestimates how meaningful his actions are, and how much they mean to Jemma - and how disappointed she is in herself for not being able to live up to her own expectations of “the perfect date” on her first night out.)