One of the optimizations done by optimizedTNT makes TNT not push other TNT that are in the same position, because if the TNTs are on a block the push has no effect.

However, there is no check to determine if the TNT is actually on a block, which breaks the behavior of TNT that is in the same position and in the air.

To replicate:
/log explosions
/script run loop(3, spawn('tnt', x, y, z, '{NoGravity:1}'))

• Without optimizedTNT, the TNT all explode in different Y positions after being pushed by the other explosions.
• With optimizedTNT, the TNT all explode in the same position.