Without knowing the detail, it's almost certainly a statistical model. Call it ML if you like. GDP nowcasting models take contamporaneously observable variables like foot traffic as features and GDP - which is observable only with a several-month lag - as the target.
The same caveats as with all statistical models apply. We only see the relationship as observed in the past and it only captures correlations (clearly, foot traffic in and of itself does not meaningfully cause GDP).
The same caveats as with all statistical models apply. We only see the relationship as observed in the past and it only captures correlations (clearly, foot traffic in and of itself does not meaningfully cause GDP).