This may be true, but from my understanding it's only company policy not law, i.e. won't get in trouble, not breaking laws.
USPS is different in that it is law and you could theoretically face penalties.
TABC makes it very difficult(not impossible) to ship alcoholic beverages from licensed distributors like buying online, but as far as I know doesn't regulate private shipments.
Unmarked package, should be fine. You run into similar situations with shipping firearms.
This is what I found from research back when I was a homebrewer, and trying to get good deals on single malt whiskey. As always, look up info before acting on internet advice, my info is at least a few years old.