Actually, I'm going BOS-ORD-NRT-HKG, on AA as far as Narita and CX on to HK. I would arrive HK at 2225 on a Saturday, in plenty of time, I think, to catch the 2340 CX-operated flight 749 to JNB.

I thought the rule sounded fishy. I ask my TA to check again - she's usually wonderful.