It's so true about the hot flushes coming and going. That is one of the reasons that it is very difficult to know what (if anything) genuinely helps to ease the symptoms.
When I first started getting hot flushes, I tried various herbal 'remedies', including black cohosh, but saw no improvement.
This time last year, the hot flushes and night sweats were so bad that I finally (after 3 years) asked my GP for HRT. However, in the 2-week wait to see her, the hot flushes eased off slightly, so I decided not to start taking the HRT that she prescribed straight away. That was the start of almost 6 months of only occasional flushes and less severe night sweats.
If I had started taking the hormones two weeks earlier, I would have been convinced that they were to thank for my relief, and the same would have been true if I had tried another herbal remedy at that time.
In other words, there is a lot of room for coincidence.