Are the risks of hormonal therapy for premature menopause the same as after natural menopause?

No, the risks are less for women who have had a premature menopause and are using oestrogen before age 50. This is because oestrogen would normally be present until age 50 so oestrogen in cases of premature menopause is simply being used as a replacement strategy. This is true “hormone replacement” (or HRT) whereas hormone treatment after the natural menopause (age 50) involves using hormones when they are not normally present and is therefore now called Menopausal Hormone Therapy (MHT).
Hormone therapy for premature menopause does NOT increase the risk of breast cancer before the age of the natural menopause.