Parry sure. Blocks generally are super low percentage too. With a parry you are intercepting at the elbow, a much closer target, and your hand doesn't need to move far assuming you have your guard up.
And while your presented scenario would and could work in theory..it's still problematic in a couple ways. First, anyone throwing a combo like that will have at least basic boxing, which means the feet will probably be moving. This means if you eat a jab to the face, and are able to continue your momentum at all after that, much less with any accuracy (unlikely), he will likely be off line when he throws the back hand.( Generally boxers will step in diagonally to the outside)
Secondly the whole purpose of the jab cross is to hide the cross. If it's done well you won't see it much less be able to intercept it with your palm all the way back at the shoulder.
All in all this is one of those things that looks neat during cooperative demonstrations, but good luck pulling it off against resistance.