I don't know how true that could be unless your work for the post office and actually see the process. I've ordered from IDEAL for several years including the last 2 and all of my chicks arrived fine. It could be that I am only a few hours away, but one of the regional post offices is an hour away and always call me to give me the option to pick them up the day before or wait the additional day. I guess it all depends on the distance. I've only ordered once from Murray and all the chicks died within it 2 days. They arrived in pretty bad condition, but once again they traveled a long distance. IDEAL doesn't ship birds in bad weather as far as I know. Plus the weather is unpredictable. It could be sunny in TX but not in another state.
It does depend on the distance, and on the post office technology between the sender and the receiver, and also on the services you purchase for that package.
You are welcome to look at the process, yourself, on the USPS-published YouTube videos.
Here is the most recent package processing video I could find:
Look at minute 8 to see packages go flying off the conveyor belt. Imagine chicks or hatching eggs in those packages, because if you don't pay for special handling for that package, that's how it could be processed.
I remember the old days when chicks arrived the day after they were hatched. Now they arrive two days or more later than hatched. Chicks are fine with a day without food and water, but two days is a big stress, and they are not designed for that.
I don't know about you, but I have called the hatcheries and asked to pay extra for next-day delivery. Murray McMurray, Stromberg, Ideal and Cackle all said no, it's too complicated for them to track which chicks should be sent next-day.
So, in very cold or very hot weather, or when there are delays in shipping, many chicks from hatcheries will continue to arrive dead or in heartbreakingly poor condition.
The fault is not with the USPS. Their Special Handling service is designed to make a safe trip for chicks, and for hatching eggs, too. I have used it, and it works. And it is insured. The fault is with the hatcheries in failing to send the chicks safely, and the fault is with us for not insisting on safe shipping.
Personally, I think it's just a matter of time before hatcheries who don't do next-day special-handling shipping will fall by the wayside.
Sadly, in the meantime, there will be a lot of dead and damaged chicks, and a lot of heartsick people who receive and have to care for those chicks. And people in these forums will continue to be called on to respond to new and bewildered chicken owners trying to fix what went wrong.
Stepping off my soapbox, now.