This is just not true for everyone. There are trans people who live as stealth. It’s generally easier and more common for trans men than trans women. There are plenty of stories of trans people being outed and having their whole lives turned upside down, being fired from their jobs, being ostracized from their social circles , etc. This could not happen if it was impossible to pass.

I cannot stress enough that I have met people who literally do pass, whom I would have never known were trans if they had not told me in confidence as another trans person. And I am more aware than most people would be because I have in interest in looking out for people who are like me. Most people are not thinking about trans people as much as I am

There are also cis people who do not “pass”, who get casually misgendered. There are even masculine cis women who get harassed for using the women’s restroom because they look like men. All of this can And does happen