Try watching it again and this time watch watch Christensen actually does. He's playing someone who's extremely nervous and adjudicated, but that adjudication is not directed at Obi-Wan. He has to maintain that state because in the next scene he meets Padme and he still needs to be in that state. It's a valid acting choice because he's maintaining his character's emotional continuity.
Also consider that the way they behave around each other in the speeder chase and in Palpatine's rescue (and 80% of TCW come to that.) Snarky banter is kind of their whole thing and there's no lack of respect in it for either of them. They're brothers.
Obi-Wan is intentionally provoking Anakin into biting back to try and distract him so he can relax a bit. I mean, do you really think he'd forgotten that *he* was the one that fell into a gundark nest? Unlikely.