Over time I am sure the expanding, contracting, are what contribute to the ends falling apart, the o-rings blowing out, that and I've heard some coolant systems can get over-pressurized, and that the Dorman o-rings can't take the pressure so they leak, I am not sure how true that is, but when I replaced mine when I did my UIM/LIM job I had it leak on me when revving the car while at normal operating temperature, I removed the elbow and could see the o-rings that already looked a tiny bit too small compared to the AC Delco o rings, had shrunk, or the outer edge had flattened off, and it was allowing the elbow to have a small leak, I replace the o-rings with AC Delco ones and have had no leaks since.
Aluminum should fix the warping/blowing out issue with the old elbows that some would experience, but if the o-rings used are prone to fail, then I am sure some of the elbows would still develop leaks.

I am not 100% sure, but I've always been told the ones GM sell are from a different manufacture, it may well be that they are all made by the same company, I just cannot see why they both do not have the same o-rings, I am almost positive the elbows from GM had AC Delco o-rings.

I'm not sure either, but I know we all must agree on one thing, its about DARN time they came out with something different right?!

Most definitely!

where can we buy he new designs?

The only place I know of that stocks them so far is RockAuto.

DORMAN Part # 47065hp
More Information About this Part #12565082, 24503423} Elbow; Aluminum; w/O-ring Seal; Includes Upper & Lower Elbow
Category: Heater Hose Fitting

15.54 total shipped.