Hmm, that's weird. The placement and type of split is strange, too. I've had lengthwise splits in revolver cartridges, but never across. Plus, it's well above the case head, not near the edge of the die marks.

I've got some 460 S&W Hornady brass that I've run hot 4 or 5 times with no issues yet. Probably just a bad case, but I certainly can't fault you for wanting to go with Starline.