Because IPSF method is different than anySIM.

i know but it doesn't make sense that their software works only with AT&T.

What would happen if you changed the permissions of the lockdownd file to read only temporarily.

Then applied the firmware update, is it possible the phone would upgrade but remain activated?

Any thoughts?

I think that IPSF means that if u have ur phone activated with Att u can change the sim and it is still working but the problem is if u dont have it activated because u can not activate it again with the new sim.