Unlike TNT blocks where setting off one block continues to pass on data on who caused the explosion to any other TNT block, TNT Minecarts don't follow this behaviour.

Steps to Reproduce:
1) Build the setup as shown in the attachments. The arrow on top of the oak plank is an arrow shot from a bow with the flame enchantment.
2) Break the wooden plank to cause the first TNT Minecart to set off from the flame arrow
3) When the first TNT Minecart blows up, it results in the other TNT Minecart to blow up and you to consume a totem from the first explosion. In the second explosion, you will die.

Expected result:
"Player was blown up by Player"

Observed result:
"Player blew up" showing that the initial minecart had not sent the data of who set it off to the second minecart.