They aren't useless. They had a 99.99% probability of winning. What ensued was an exceedingly unlikely even. Blowing a 19-point lead in the fourth happens 1 in 10,000 times. This was that one time. Just like them blowing a 3-1 Finals lead is an exceedingly rare event. It hardly ever happens, but it happened this time. It is unlikely to happen again anytime soon.
Did they have a 99.99% chance of winning?
One issue I have is that such metrics are used as forecasts when in fact, they are not. In other words, one can make a predictive assessment based on past data to approximate the likelihood of some past event that doesn't actually speak to the probability of some
specific future event happening; i.e., the difference between forecasting and prediction.
In other words, while it is reasonable to assume that teams in a general sense blowing a 19 point lead in the 4th quarter happens 1-in-10,000 times based on past events; it is not reasonable to assume that the Warriors 19-pt lead had a 99.99% chance of holding up against the Grizzlies last night.
There's
a lot more there to be considered other than how often teams come back from 19-pt deficits in what would usually amount to extended garbage time. This game was nothing like that and was competitive throughout the 4th quarter.
The metric that was used was likely not a forecast model to take such things into account; so that's one of the reasons it was and is rightly ridiculed.
It's a perfect example of the widespread misuse of statistics.
p.s.
The Warriors were up 14-pts against the Cavs in the 4th quarter; they lost.
The Warriors were up 19-pts against the Grizzlies in the 4th quarter; they lost.
The Warriors blew a 3-1 lead in the Finals last year.
They've melted down in numerous 4th quarters this year.
They aren't just monumentally unlucky; the general statistic regarding historic trends is simply being used incorrectly. It is predictive of past events, it is not forecasting the probability of specific future events between two specific teams.
tl;dr: The Warriors did not have a 99.99% chance of beating the Grizzlies when the 4th quarter started last night.