Hmm no I don't agree with that. Pacey wasn't really that into Joey in S1, he just saw her partially naked and thought ooh actually yeah. Before that, there had been no interest in her whatsoever. I don't think there was anything there that Dawson should have thought later on, oh yes he was interested. While Dawson's behaviour when he discovered them, I can't blame him for being surprised at all. Pacey had shown no interest in Joey before aside from that one episode and that was over in a flash.