Thank you for the question.
You'll know that the terms are not defined in the Criminal Code. They are defined in various places for different purposes and their meaning is understood. Admittedly, “gender expression” is a very broad term. It's about how one expresses one's own gender to the world.
I've acknowledged in my comments that this amendment would broaden the definition, and it's my understanding that this is for evidentiary reasons. I also note that the terms “gender expression” and “gender identity” are used in other places in the Criminal Code and in human rights legislation, and they do have meaning in law.
I hope that answers your question.