Thanks for this feedback--
It's very accurate that 13Fs do not pick up hedge fund activity such as short sales and derivatives. 13Fs are not necessarily comprehensive of all of a single hedge fund's positions as certain funds sometimes make amendments at a much later date.
Hedge funds, particularly activist funds, do sometimes try to conceal the stocks they buy - usually by using derivatives which have different disclosure requirements. However, it is pretty rare for a hedge fund to be long and short the same stock unless they are doing it for tax reasons - this does not happen often. Going long a stock to create confusion about a short position (which is not disclosed) does not happen in the wild.
We believe that "knowing" in the aggregate just the stocks that managers are long has value. It is noteworthy that equity long/short strategies take a few quarters to materialize so using quarterly data is still valuable (hence we have excluded hedge funds that follow a short term statistical arbitrage strategy with many positions and very high turnover).
I think there is value in what you are doing, as long as everyone knows what context to put the information in, and realizes that they may lack significant additional information. In the wild, HFs are actively engaged in sending misinformation to the market in a number of ways, by running different sides of a trade through different prime brokers, etc. I have no doubt that some of them are sending information via their 13Fs that is meant to be misinterpreted.
We ourselves used to track the number of "smart money" investors in biotech stocks like BLUE (bluebird bio) in Excel spreadsheets. The motivation for Navlio was to make this easier and more functional. Using BLUE as an example, the number of "smart money" investors increased from 2 to 10 before its stock price increased over 6x. We used Navlio to find other stocks like BLUE that hedge funds were buying and invested in some of those as well. If you want to actively buy stocks, this is a way to complement your research.
Navlio does not use proprietary methods to rate stocks or promise outperformance. Rather it is a navigation tool to make publicly available hedge fund data more accessible. Whether you believe that using this subset of hedge fund data can help you invest better or not is up to you. But at the least it has the potential to give you a sense of what professionals are doing in and around the stocks you are looking at.
Hedge funds, particularly activist funds, do sometimes try to conceal the stocks they buy - usually by using derivatives which have different disclosure requirements. However, it is pretty rare for a hedge fund to be long and short the same stock unless they are doing it for tax reasons - this does not happen often. Going long a stock to create confusion about a short position (which is not disclosed) does not happen in the wild.
We believe that "knowing" in the aggregate just the stocks that managers are long has value. It is noteworthy that equity long/short strategies take a few quarters to materialize so using quarterly data is still valuable (hence we have excluded hedge funds that follow a short term statistical arbitrage strategy with many positions and very high turnover).