I think it really depends on the market, but I have lots of proxies for order flow, some of them clever, some laughably simple. Maybe they're harder to understand than this type of software.
For example, the ICS market (long/short yield curve spreads) greatly determines order flow in the rates market. NYSE traded volumes really affect price moves in stocks, and vol marks heavily influence flows in mega-cap stocks. Then there are futures basis spreads, intermarket quotes and volume weighted prices on cross-hedged index positions. VWAP and momentum algos in fx futures, etc.
That software, if it does work, is easier to understand than the others I mentioned.
Bottom line is, flows originate from different places in each market. Also, the off-exchange and unlit trading is substantial, so listed volumes have to be read in multiple ways.