The problem is the style of the bag, it could either be;
1 - There is nothing in the front compartment (where the smaller zip is) and so the pressure cooker device in the large, main compartment is simply poking through both the main bag and the front pocket, or
2 - There are normal items in the main compartment and there is a small item in the front pocket as well, which is giving the impression there is something big in the bag, because the item in the small front pocket is pushing against the fabric.
It's pretty hard to differentiate the two IMO.
I don't really buy the theories myself, if you're going to walk around in huge crowds, full of cameras and whatnot, you don't make it perfectly obvious you're carrying a huge device in your bag - it would have been concealed more effectively.