They're probably using lithium ion. Lipos are quite different. They're a lot less stable than lithium ion.

A lipo will have a measure of gas dissolved into the cell of the battery. So, heating it up or a rapid drop in air pressure can release that gas and cause the pack to puff.. Kind of like a scuba diver coming up too fast.

That is my understanding.

Ship it ground... pack it well...

They will not ship a "damaged" lipo under any circumstances though. That is why often warranty claims are done with pictures.

take 1 commercial jet, loaded with say 300pax

betcha you'll find onboard...

300 mobile/smartphones, 1 lipo in each
50-100 USB power booster, 1 lipo in each
100 laptops, 1 lipo in each
100 tablets, 1 lipo in each
100 iPods, 1 lipo in each
100 digicams, 1 lipo in each + some extra spares
25-50 DSLRs, 1 lipo in each + usually extra spares
25-50 MiFi devices, most have lipo
25-50 handheld GPS, 1 lipo in each
-----------
heck that's like near 1000 lipos already

Items in the passenger cabin have the benefit of a climate controlled pressurized environment. I also imagine that the bulk / volume of the battery can come into play at some point as well. And I have seen cell phone batteries puff.

If you ship a lipo just declare it properly and let them handle it.

FYI, the cargo hold is pressurized. It would be impractical for structural reasons to pressurize half of a cylinder. Look at the cross section of an airplane fuselage. It's cylindrical. There's a reason why pressure vessels are round, and the reason is hoop stress. Trying to reinforce the large flat floor to withstand the differential pressure would add significant weight to the plane and be completely unnecessary. Look at your air compressor tank. Now look at the fuselage of an airplane. Look similar? Yeah, because they're both pressure vessels.

Also, the cargo holds are not heated, but they are not typically below freezing. There are live animals down there, and they don't want everyone's shampoo and stuff freezing and leaking all over the place.