I think that if you are naturally menopausal, you gradually (in an up and down way
) stop producing oestrogen in the ovaries and the ovaries limp along for a while after menopause. Some is made in the place it is used from your fat cells (oestrone rather than oestrodiol). Everyone is different, so some will limp along for longer than others.
If you have a surgical menopause, then it all happens at once and you go straight to the making it stage. Same end, but you get there all at once.
A lot of symptoms are due to the ups and downs of perimenopause (or the sudden down of surgical menopause). HRT gives you less oestrogen than you would have naturally so it is less of a steep cliff, and you can reduce gradually over time. So if your problem was flushes, these can be managed more gradually.
Long term effects are calcium loss from the bones (which is on a slow downward trend, happens more rapidly over menopause, then returns to a more gradual downward trend, and you can't get it back by eating more calcium) and atrophy of the reproductive bits which are not needed any more
(which can have knock on effects of the uro- bits which are part of the -genital bits). Both these are well worth delaying, especially if you are starting them early on
If these effects kick in early at 45, and you live to 85, that is 40 years with thinner bones for your age, and incontinence meds/antibiotics/pads.