Well, the reduction in available credit will only last a little while (maximum 1 month but usually much less).
Why? I find that more difficult to explain. It's probably something to do with a floor limit. Every credit card merchant has a floor limit. Any sales above that limit must be referred to the credit card company for authorisation. Most airlines have their floor limit set very low - USD 1 is not unusual (I would go so far as to say it is usual).
There is a function to simply verify that the card numbered offered is not on a hot list (stolen, used fraudulently etc). My guess is that cards issued by Chinese banks are considered at greater risk (though that sounds terribly negative) than others so a pre check is made. Quite why that causes a USD1 reduction in available credit I'm not sure.