[lawpoop]

I think what is meant is that you can't have a subjective experience of two different consciousnesses at the same time.

In other words, one of the properties of the subjective experience of consciousness is that of a unified whole.

In the experiments you link, the two consciousnesses are not aware of each other, and presumably(?) don't experience the other, thus they are two separate, individual consciousnesses, each experiencing themselves as an indivisible whole.

In other words, these brains host two separate consciousnesses, just like our two skulls host two separate consciousnesses (in two brains). Whatever wiring links up aspects of the brain that gives the perception of unified conscious has been sundered.