Agree. Poor form really. It means that they can take the BTC that you have invested there and deposit it on an exchange which does support BCH and just pocket the BCH. Which is what I'm sure they are doing.
It would have been nice if Luno could have provided for BCC but I don't think they are doing anything audacious. The amount of BCC you will have at the onset of BCC is the amount of BTC when the chain is duplicated and incorporated into BCC. All you have to do is withdraw your BTC from Luno soon enough before the chain is duplicated which includes enough time for your balance to propagate through the nodes.
According to their statement BCH will be incorporated into Jaxx. All you need to do is have the BTC in your wallet during the fork. Seems the biggest obstacle is them waiting for the new chain to download as all the programming is already done.