I am lost in the WHO sex, sexual orientation, gender, and gender identity definitions

 I am a bit lost in gender/sex definitions for sports. I took a brief look at the WHO gender definition. Gender is a social construct. WHO:"Gender refers to the characteristics of women, men, girls and boys that are socially constructed. This includes norms, behaviours and roles associated with being a woman, man, girl or boy, as well as relationships with each other. As a social construct, gender varies from society to society and can change over time."

WHO defines the word "sex": "Gender interacts with but is different from sex, which refers to the different biological and physiological characteristics of females, males and intersex persons, such as chromosomes, hormones and reproductive organs." So far so good. Then "gender identity" appears as "Gender and sex are related to but different from gender identity". There is also a long sentence on inequality/discrimination. "Gender is hierarchical and produces inequalities that intersect with other social and economic inequalities. Gender-based discrimination intersects with other factors of discrimination, such as ethnicity, socioeconomic status, disability, age, geographic location, gender identity and sexual orientation, among others. This is referred to as intersectionality." here, I found a new notation "sexual orientation". Each person has at least four qualities, q, which define something in the person: sex, sexual orientation, gender, and gender identity. In such a four-q combination, what does mean “transgender”? Is that the change in the social construct as the word trans-gender suggests? But is the change in gender also the change in gender identity? The WHO clearly explains that gender and sex are related to but different from gender identity. The change in gender is not the change in gender identity and a trans-gender may change gender but not gender identity. And vice versa. Moreover, any change in one, two or three q from the total of four does not mean that the left q change.

These definitions have applied aspects. For top sportive achievements, both gender and gender identity means nothing as the social construct cannot change personal physical performance. I doubt if sexual orientation can be of special service to sports. Finally, sex as defined by chromosomes, hormones and reproductive organs is the only defining factor. Gender, gender identity, and sexual orientation (as defined by WHO) cannot change sex. Intersex persons who may or have to choose sex are not transgenders as the sex change does not imply the change in the other three q. My confusion is why the term transgender is used when applied to sports?