In Sharaie al Islam, Kitab ul Jihad, p. 315, you can read:
If the dead bodies of Muslims mix up with those of the Kuffar (during or after fight) then bury those who have small manhood.
Shaheed al-Awwal said in “ad-Durroos” (2/35) said:
ويجب مواراة المسلم دون الكافر، فإن اشتبها دفن كميش الذكر
It is necessary to bury the Muslims, not the kafir, and if there is doubt, bury the one having small penis.
Just question what kind of survey was done by these shia scholars to get this interesting qualitie of shias?