Gender-affirming care/medication more commonly given to cis people than it is given to trans people. Mostly because the trans* population is in reality very small, it just feels like there is more trans people than there really is because they are hated on so much and so loudly. The biggest problem that that most people don't recognize cis gender affirming care as "gender affirming", because the term is applied to heavily to trans* healthcare and not at all used for cis healthcare unless you are in a scientific setting. These types of experiments named here are in reality run for cis people, not trans, because hormones can effect so many things and its not very widely studied how they interact with many medications, like HIV medications.

Hormone therapy is used for a variety of reasons that are not necessarily gender dysphoria. Hormones have a HUGE effect on all aspects of your body and cis or trans* a hormone imbalance can be horrible.

Lots of cismen take testosterone as they get older because as they age their body does not generate as much as it did when they were younger. Insufficient levels of testosterone in men may lead to abnormalities including frailty, accumulation of adipose fat tissue within the body, anxiety and depression, sexual performance issues, and bone loss.

Conversely lots of ciswomen will take estrogen and progesterone to counter the effects of menopause, when their bodies start to produce less hormones. Lack of estrogen for women can lead to many of the menopause symptoms such as irritability, brain fog, hair loss, joint pain, weight gain, bone loss, hot flashes and cold sweats.

Many cancers are also hormone fed, most common would be hormone positive breast cancer. AFAB Breast cancer survivors cannot take estrogen or progesterone hormone therapy like most cis women can because it increases the chances of it feeding the tumor. Testing if they can take testosterone is still very new in the research process, considering they didn't start doing ANY hormone therapy research until after the turn of the century.

Other examples of cis gender affirming care is hair plugs, breast implants, breast reconstruction after mastectomy, any type of genital reconstruction, gynecomastia treatment for cismen, and so on...

TL:DR These experiments are for cis medical care, not trans. The only reason they were targeted is because of the phase"trans" and the phase "gender affirming".