It also has false positives. Not the authors fault, but the data source used is cached.

90% accurate is not my experience. When it first appeared and I compared its results on the LHR-SFO in J, a decent amount of the "availability" did not exist on ba.com. That may have changed if the source data is more correct now, and it could be that the level of accuracy is route dependent. Its definitely useful to give indicative availability though.