TNT blows away less cobblestone

Usually TNT was destroying an area of 5 x 5 mainly, with only a few blocks left over. Now i tried my cobblestone generator on the latest snapshot (14w21b) and I discovered that only a cross of cobble was blown away. Is the cobble stronger now? Is the TNT weaker?

I searched on the bug tracker system for similar issues but didn't find any so you guys don't need to remind of the 52% closed thread for duplicating.