After having HAL open the pod door (in the rear of the pod, facing HAL's eye) and then entering the pod with Poole, Bowman tells HAL to rotate the pod, which of course makes him and Poole visible to HAL through the window, allowing HAL to read their lips.
I can't figure out why he would take that extra step. Obviously he doesn't know HAL can read lips, so if the window were already facing HAL, that would be one thing. But he has to go to the trouble of issuing that extra command.
The only answer I could come up with is that he wanted to minimize any impression of secrecy; he didn't want to arouse suspicion by being invisible in his confab with Poole. That seems dumb, though; surely the best ploy would be to appear completely oblivious to the very concept of secrecy.
(Altogether, Bowman has shown no savvy about the ruse to this point: his initial "Hey, check out this problem" to Poole is pretty stilted and comes too immediately after the HAL-made-an-error scene, and then he and Poole keep glancing pointedly back at HAL during their extended conversation in the pod... I guess there's no reason to think HAL would see red flags in those cues, but he is supposed to be super-savvy about human interaction. That said, I think the badness of the ruse has more to do with how the scene comes off on film rather than anything intentional on Kubrick's part.)