Consider the case of finding a set of strategies governed by a particular set of parameters in a book. For instance, the Moving Average lookback period. You will see authors posting certain strategies, albeit without revealing the market/time series with which they're carrying them out on or which exact parameters they use. This is the critical information, but it is also relatively straightforward to trial/test, assuming you have the available data.
Also - the same strategy, implemented identically, can be both successful AND a failure for two different traders with identical starting capital. Why? Because one may not have the stomach for a 50% drawdown in the equity curve, despite the fact that had they waited, a "big swing" would have been around the corner. It is as much about preferences/tolerances as it is about the actual rule set.