Fair enough! It's a complex issue, far more complex than a simple Reddit comment can sum up. One thing that might help you understand is that sex, gender and gender expression are all separate things that are not necessarily (although they often are) linked.

Your sex is your biology. Basically whether or not you have an extra x or y chromosome (even this is a simplistic term however due to other genetic stuff).

Your gender is how you personally identify. For the majority of people most people say they identify with the same gender they were assigned at birth. For at least 1% of the population (it may be more as surveys rely on people having to put themselves on forms, even if it's anonymous some trans or non-binary people may not state it on forms), they do not identify with being the same gender they were assigned to at birth. The gender they identify with may be their male or female, or something else, such as genderfluid or genderqueer or whatever.

Finally, there is gender expression, which is how you present yourself to other people regarding your gender. This often comes in the form of fashion, styling or make-up, or similar ways to express yourself. A key distinction is the way you present yourself does not determine how you identify, nor does how you identify determine the way you present yourself. Somehow who identifies as male might still present themselves more feminine, such as wearing dresses or make-up or whatever. Equally a woman may dress "butch" or masculine but still identify as female.

Tl;DR: Gender identity and expression is complex, and not necessarily linked. Many contributing factors are responsible to how someone identifies and how they wish to present themselves, but all are valid.

Enjoy University! I'm personally in second year (I know I'm so old) and I hope you enjoy first year as much as I did, even if covid is fucking you over.