Truly buying at a bearish market period is an added advantage towards investors accumulating of their bitcoins because they'd buy cheaper on a gradual while stocking on higher volume and keep holding until the market skyrockets.
Buying at the bullish too is a good one because new ATH would always be expected for long term Investors in order to account profits.
It's just about eliminations of FOMO and regardless that you'd miss out of investing lately or when the market price seems scary high.
It's not that it's an advantage but this is how investing originally works and that is to buy low and sell high, and I think methods such as DCA are only invented lately. By the way, DCA is the act of buying at any price and not all times there is an ATH, so this was still better than buying during an ATH because we have more chances of seeing an increase than a decrease and that means more profit for us.
People are FOMOing when the market is in bullish period, especially if there are new ATH that have been recorded but it's fine if sometimes we can buy during it because it was still not intentional and we also have our own personal goals.