No it is not neccessary and extremely stupid as he could have broken his phone.
Pwnage ONLY works on 1.1.4.
You have to pwn the phone FIRST so it has the pinepapple logo.
Then you can restore using the custom IPSW. Sometimes you have to put the phone into recovery mode first before the restore works.
If your still getting 1603/4 errors then try a different USB port/computer.
ZiPhone was totally unecessary and defeated the point of using pwnage - which is to use a safe fully reversible unlock method on your phone - and although pwnage can reverse ZiPhone now its definately not safe!