I'm not familiar with the definition of “organ” in the Criminal Code, but I don't think we should stray too far from ordinary English language understanding or medical understanding of the terms, and “tissue” is a concept distinct from “organs”. It is possible, I suppose, to define “organs” to cover more than what is ordinarily understood as organs, but that would raise the issue of a further amendment.
I think that if we have “organs” and not “tissue”, we're stuck with “organs” and not “tissue”. I see that as not necessarily a problem because the bill.... I mean, no matter what legislation you have, you can always think that there is something you can add that might improve it, but there is nothing wrong with the bill as it stands simply because “tissue” is not there.