Yes, as they are entering the new production cycle for their 28nm chip (Bitmain S3) they are just selling off the "old" components without bothering to do full assembly and sourcing of cases / PSUs.
They probably finished the S2 production cycle at the beginning of this month, selling the built units until now.
As their 28nm production starts, it is very easy for them to first send only "blades" ie. upgrade modules to customers.
If you already own a Bitmain S2 you can then easily upgrade it by swapping out the modules and voila you have your new and more efficient miner.
As their assembly starts to gain speed again, i am sure they will also sell complete S3s.
That's interesting. I guess it's nice thought that by buying this kit you can pick your own power supply, but I don't think I'd be up for making my own case / fan braces.