Oestrogen dominance seems to be the thing at Cemcor in Canada
http://www.cemcor.ubc.ca/, where it is asserted that the theory that you need oestrogen during perimenopause is wrong, because oestrogen is actually at a higher level than normal. This should be treated with progesterone.
I am sceptical, myself. From what I remember of my human biology lessons, many years ago, there are complex feedback mechanisms. We only produce progesterone after ovulation, from the ovary where the egg has been released, so it is not in your system all the time, unless you are pregnant (or on the pill). And anyway, it gives me terrible constipation, so I do have a personal aversion to the idea
Normally, you would produce oestrogen in the first half of your cycle, while the follicle is ripening in the ovary. This peaks as you ovulate. Progesterone is produced by the corpus luteum, which is what is left in the ovary when you have ovulated, and this produces a spike just after ovulation (you can measure this as a small temperature rise, if you chart your cycles). After a couple of weeks, this degenerates and the ovaries stop producing progesterone and oestrogen, their levels crash, and you have your period. (unless you are pregnant, then hormones from the fertilised ovum keep this going until the placenta takes over)
During perimenopause, the follicles in the ovary are a bit knackered. So sometimes, the FSH will be stimulating the ovaries to produce oestrogen and the follicle does not ripen, the levels go up and eventually crash and you might get a bleed, without ovulating. Or not get a bleed and start another cycle. Sometimes, it might be more prolonged, or shorter. Sometimes, the ovaries might not respond at all for a while, then start up. You might ovulate, but the egg is a bit past it, and the corpus luteum and bit past it and you get a sort of progesterone rise, or you could get a big one! Or you could ovulate normally for a while. So your oestrogen levels can fluctuate from very high to nothing, and progesterone levels are intermittent.
The possiblilities are endless. If you take progesterone all the time, it might help reduce the bleeding, and proliferation of the endometrium, like taking norithisterone does, or mirena coils but minipills, which have less progesterone don't usually have much effect. Smaller amounts may stop you ovulating when you are close to menopause, but I am not sure that helps.
I am sure that conventional hrt is fine - it has the progesterone which stops the endometrium proliferating, and the oestrogen which stops you hitting rock bottom. I am sure this helps your body's feedback systems stop levels from going sky high once you settle on it and help stabilise your levels.
This is just my take on it - hopefully someone will come along who can remember stuff