A DVD image is unfortunately not available for FC5test1 due, but the plan is have it for test2. CD and network installation are available. Please read the Important Warnings below in this announcement for more details.
Most likely, you just downloaded a big package with all the isos inside.
Short answer, it won't create a bootable DVD image. You have to burn the 6 isos's or mount them as loopback and install from them.
This is one way to create a bootable cd with K3B. However, it won't work for creating a bootabel Fedora DVD, since all the files are inside ISO images as you pointed out. More so, the install application most likely has some installation paths hardcoded that it won't be able to find.