A bull market is a period of time when the stock market or crypto market is rising and is expected to continue to rise. This is a time when investors are optimistic and confident in the economy, and are willing to buy stocks.
No investor venture into investment while the market is on a bull track, if they do it simply turns to a bear traps because you don't know when the bull is expected to end so they are always vigilant to take profit and maximizing the chances of the bull run. However during the bear market investors always wait to see the bottomless part of the market before venturing into investment, and they buys in a larger qualities holdings wait for another bull run time for them to sell and make substantial profits, imo.
Both of you guys are correct, perhaps you misquoted @ammo121810. What investors are interested in is the trend of the asset, and the investment could start when the asset has bottomed well and validated a reversal. Yet, it could only be ascertained when a new trend is formed which the guy is talking about.
However, investment practices could vary, some investors might even purchase the asset when it has not formed a bullish trend but must have been reasonably low. Such investors are taking more risk too since no one knows the exact level at which the asset would reverse its trend. While other investors make sure that a new trend has formed before purchasing the asset.