Without entering too far into the realm of speculation, I think that's correct. The fact that Parliament has chosen not to include it would not be interpreted to mean that expression is not covered.
To get back to your earlier question, obviously it's up to Parliament to decide what it chooses to do, because, as Ms. Stone has mentioned, expressive elements for other grounds are covered without being expressly mentioned. From the perspective of consistency in drafting, to add a specific reference to gender expression when that is not there for the other grounds could create an apparent inconsistency in the way that the grounds are treated in the act, but again, it would always be a matter for the tribunal, and eventually for the courts, to interpret the significance of any such discrepancy.