This is the exactly true answer! This is normal business pract

This is normal business practice in most countries. It totally makes sense.

只给我报销在国内的机票, since the travel exp. in 国内 is for business purpose;
不给报销回国的机票, since u were on vacation,来回中国的机票 exp. were for personal travel intention.

Think this way, if there was no such things of "拜见客户", you at least pay the 来回中国的机票 exp by yourself.