Spawners do not drop experience when blown up

The bug

When mined with a pickaxe, spawners drop experience. However, when blown up, they do not.

How to reproduce

1. Use commands to place spawners
2. Break one spawner with a pickaxe in Survival
3. Use TNT to destroy another

Expected results

The spawner would drop experience in both cases.

Actual results

Only manually mining spawners drops experience - explosions do not.