I think your describing a "hesh" round and this was not used in tanks during ww2.
Also do u have any sources for panthers(or any tank) using HE in the "mine field" manner you describe and want this delayed HE for.
Also my science is fine. If an HE round buried in the ground explodes then its energy (shock wave) will be mostly absorbed by the ground. Thus having less effectiveness on targets above the ground.
Little experiment for you. Hold a firecracker in an open palm vs bury it in dirt and place your hand near it.
See what hurts more.
