You are correct in that such a low dose for a short period of time is unlikely to have major problems, but HRT is not a risk-free treatment. It increases risk of heart disease, stroke, blood clots and more.
In studies of post-menopausal cis women, that's correct, extended use is associated with those things. (Also, I think some of those were done with Premarin, which is no longer widely used?)
There has been unfortunately few studies done on transgender people or on young people. (I welcome any links to studies you have!)
