I was initially skeptical of this arrangement from the picture, but I just now figured out why.
For a given thickness of shell, a smaller surface area can withstand more pressure just because less area is exposed to the pressure. This helps reduce breaking on impact on relatively soft surfaces. Now add support to that smaller shell in a foam cup, and the break on impact is reduced again.
Since we are talking about a long distance round, this would be a significant problem. I can see these breaking at regular paintball ranges, but with better accuracy. I will be interested to see how these break at distance.