TNT not igniting and oversized

I noticed that when TNT is triggered in high amounts and then covered in water just before exploding, it remain frozen and does nothing but remain a useless, white, oversized block. As compared to a normal TNT block.

To reproduce try:
1. Open a flat World
2. Use the command /fill 1 5 1 100 200 1 tnt
3. Then /tp @p -2 5 -2
4. Then light the TNT wall using flint and steel
5. Wait a few minutes and a some explode
6. Then do /fill -2 4 -2 102 202 2 water
7. Fly about and look for the broken TNT as seen in screenshot