Hence the reason why the hashrate decreased in the first place to cause a "buy" alert.
The only times were during bear markets and it could be a coincidence that during those bear markets which caused the "buy" signal we ended up reversing.
That is not the case, look at the chart, half or more of the signals did not trigger the way you describe them, miners don't capitulate only if the price dips, the mining business is way more complex compared to the average HODL business, miners can capitulate on the way up or the sideways market just the same as they capitulate on bear markets, there is a ton of explainings and reasons on why these facts are valid, I know it's hard to understand that miners can capitulate even when the price is going up, but it happens and it has happened before, and there are solid reasons for why that happens.
I used to take the position that price determines hash rate, period. After hearing the (somewhat convincing) opinions of some OG miners and researching price vs. hash rate correlations over different periods, I am much more agnostic on the subject now. Impossible to say it's 100% this or 100% that.
I would have been surprised if you sided the herd into taking anything else but this, looking at the charts for so long and analyzing the fundamentals of the market makes you see things the average joe can't see, the correlations between hashrate and price in both directions is one of a lot of things traders observe.