I found the following language in Citi AA Exec benefits fine print (sorry cannot post an URL to the pdf file since this is a new account..)
WHAT’S NOT COVERED
Coverage does not apply under the following conditions:
■ The Covered Traveler(s) is delayed due to a missed connection of their Common Carrier, but the delay that caused the missed connection does not meet the required time period of 6 hours.
I don't see such language in other credit card benefits. My understanding is that, for example I have trip from A to B, then B to C. The flight A to B got delayed for 3hr, therefore I missed the flight B to C. I eventually got to C only 8hrs later than planned. In such situation I won't get trip delay coverage, because the delay of flight A to B, which
caused the missed connection, was only for 3hr which is <6hr. Therefore, to make sure I get covered, I should always plan for >6hr connection time at B, so that any delay of A to B that's <6hr won't cause a miss-connection.
Is my understanding correct? Thanks for any advice!