The mini-pill isn't progesterone.
Progesterone is a hormone made by our own bodies. The only reliable drug we have which is progesterone, is utrogestan. Utrogestan does not override your own cycle or body, because it isn't powerful enough to (unless you take a huge amount of it).
The mini-pill is a progestin. This is a manmade synthetic hormone which has made side effects (increased risk of breast cancer, affects lipids and cholesterol, and more). It overrides your own cycle, typically prevents ovulation, and actually reduces production of estrogen. Which is why it's used for women with endo - because it suppresses estrogen.
Last thing you'd want to do if you are having low estrogen symptoms, is to be on a progestin-only. It's just doctors with no clue what they are doing, mucking around because they don't need to be the ones suffering horrendous symptoms for weeks as a result.