Since gender is being used more and more frequently by scientists, health professionals, politicians and others when what they actually mean is sex, it's only a matter of time before people propose that the Equality Act be updated to change sex protections to gender protections to reflect how language has changed and is currently understood.
Sex impacts how we respond to drugs, how the world is designed around us, even how we have heart attacks. Gender has no impact on any of those things it's all about biological sex.
For example, only one out of eight women will encounter similar symptoms to a man experiencing a heart attack. Because women have heart attack symptoms different to men, women's heart attacks are considered atypical heart attacks (unless they are that one in eight) leaving them often to be ignored. Women's symptoms include headaches body pain stomach aches et al whereas men typically feel a surge of pain down their arm accompanied by chest tightness without any of the aforementioned women's symptoms. Women get brushed to the side or ignore their symptoms when they're having heart attacks because they're told that's not how people experience heart attacks.
Every civilization currently standing used man (male) as the default for the design of most things from government to medicine to business.
There isn't even a crash test dummy that represents us for crash tests - it's a smaller version of the male dummy but doesn't represent the differences in our internal structure which is affected in real crashes by seatbelts, airbags, and structural protection (frame, steering wheel positions, pedal distance from seat et al). The fact that I have to push the seat 8in closer to the wheel than an average sized male puts my body at a significant disadvantage in a crash compared to any average size male body.
The seatbelts we currently have (across the chest and across the waist) are dangerous for pregnant women (better than not wearing a seatbelt in most cases) as they aren't designed with the pregnant female body considered.
Men are in the default position for humans in relation to design... not because they present male (gender) but because they are biological males. All of the things designed with men in mind benefit men that present as women because they have male bodies regardless of what their genitals look like. They have male hearts (larger) they have male lungs (larger/more capacity) they have male muscle and bone structure, and they do not have the space that we have between our ribs and hips because women's bodies have room for our larger reproductive organs. These are facts these differences not subjective things - they are what they are due to sex.
I haven't been sexually harassed or assaulted because I present as female (gender) it is because I am a female. I haven't been fighting my way to the top because I present female but because I am female in a male-dominated profession. I didn't go to some doctor and have boobs sewn on or had a penis removed/inverted or attempted to adopt stereotypical perspectives to 'present as a female' I have large breasts and a vulva/vagina/cervix/etc. because I was born a female and went through female puberty. Regardless of how I dress it's very obvious that I am a woman, everything about my body screams woman whether it be profile or fully in view.
I have a right to call myself a woman and know that it sets me apart from men, I have a right to spaces without men in them, and I have a right to my own bodily autonomy as well as language to describe myself.
TRAs like to put me in their bucket because I don't have children so they like to say that they're women like I'm a woman. They are attempting to strip away my humanity and deny me as a 'real woman' outside of their definitions. I don't identify as anything I just am a woman and all the other words used to describe who I am are impacted by being a human female.