He was cursed in 1898, and the Boxer Rebellion scenes take place in 1900. Also, Angel isn't bored in those scenes so much as distinctly uncomfortable and anxious, trying to pass it off as the same cool indifference he showed as Angelus, so that Darla, Spike, and Dru wouldn't think he was any different. Seems it worked on Spike and Dru, but Darla knew him far better than either of them and wasn't convinced.