Craftsman build with thrown bomb

My friend tell me, many Craftsman in Rohan build level with thrown bomb, That real thing or not?

I playing in Rohan with Hunter and in my country play with Craftsman (Playwith server TH).

I try using thrown bomb for build level, I found it low damage(grenade) and skill casting is very slow, damage 4000 and Area Destruction is 5000+ higher damage than thrown grenade.

Thank you,