If you'll recall fairly recent history, nodog, bow companies were pretty much forced into warranting their bows to 5 gpp because their idiot marketing people were advertising IBO speeds at 5 gpp. If they had their druthers, I'm sure they'd much rather still have their warranties at 6 gpp...
Except for those guys at HCA who are playing with fire and trying to reclaim some market share at 3 gpp.
If you'll look at the actual AMO specifications for testing bow speed, ASTM 1544-99, you'll find they have two arrow weights, the old standard and a new light standard. 60 lb draw, 30" draw length, 8 gpp for the standard, 60 lbs, 30" and
6 gpp for the light standard. They introduced the light standard in 1999 and, if the marketers had advertised speeds according to AMO specs, warranties would still be at 6 gpp.
Problem is, they couldn't really fluff up the 'wow' factor at 60 lbs and 6 gpp, could they. 
As for only old timers caring about AMO guidelines... Probably so. We seem to be the only ones who recall they even exist. Young pups think the only outfit that sets minimum arrow weights is IBO. All in the world IBO did was make a tournament rule to make their tournaments safer. Nothing more, nothing less. Just a tournament rule. No regard to bow performance, function or longevity. Those of us who were around in 1988 remember it quite well. They just made the rule to put enough arrow weight on a bow... to keep the speed idiots from using way too light arrows and keep their bows from blowing up and hurting people.
Even IBO is on record, disclaiming the vaunted "IBO speed" and the so-called "IBO standard". They have absolutely nothing to do with it. They never ever did have anything to do with it. It was dreamed up @ 1990 by the marketing people at, I think, PSE - taking a bit of IBO's rule book and combining it with a bit of the AMO standards - and it eventually spread throughout the industry. To culminate a few years ago in the manufacturers being forced by popular opinion that their warranties should match their advertising claptrap.
Now that's the way warranties at 5 gpp happened. No research. No science. No testing. No R&D. Just advertising. Oddly enough, bow prices increased by about 25% across the board along with the new warranties. Like you said, it's their dime. They had to raise prices to cover the increase in warranty work/replacement.
Now you should be up to speed.