Proofs for this weird statistics?

Taller people cannot take more safe positions in the army due to the vehicles height restrictions. They're also easier to shoot at as infantry and more likely to get caught in falling debris so I doubt your survival rate correlation.

Very few soldiers will be engaged in combat in the frontlines. Disproportionally many of these will be tall and gifted young men. Therefore war has a dysgenic effect

It's dont. On all occasions.

Quelle: ich habe mir diese Scheiße aus meinen Fingern gesaugt.

It's all true except the intelligence bit. Dumber soldiers actually survive more.