Our point isn't that people can't behave in ways they like more that they don't have to adhere so strictly to gender roles, expression etc. They can still, of course, act in more 'conventional' ways but the point is that they should be able to choose that and if necessary choose to break that or merely change over time, nobody should be forced to behave or look a particular way nor feel they can only be those things and that is all forever.
So it's not always exactly gender non-conformity more that behaviour and expressions shouldn't be tied to gender, and roles shouldn't exist at all. Just be you, even if most of the time that matches what society currently sees as matching what they expect, but you don't always have to.