Dying to TNT with unstable=true that has been punched by another player does not count as that player's kill

If a player ignites TNT with unstable=true by punching it and another player dies to it, the former does not get the credit for the kill.

How to reproduce:

1. Use the /setblock command to place a TNT block with unstable=true, or place a regular TNT block and use a debug stick on it.

2. In survival mode, punch the block to ignite it and stand inside it.

3. Wait to die and look at the death message.

Expected result:

"<player> was blown up by <player>"

Observed result:

"<player> blew up" (not 22w43a-22w44a) / "<player> was blown up by Primed TNT" (22w43a-22w44a)