Back in the 2000s, upon arrest it was pretty common practice for cops to page through your phone contacts to see who you knew. I don't know if Cellebrite was used back then or if it was manual but the inferences were made and the point was to map out suspects' social networks to find suppliers and upstream orchestrators they had in common.
They're doing the same thing here but lying about it. By capturing all faces associated with whatever protest is going on and mapping them to known identities (because everyone has to provide ID to do anything nowadays), they gather intelligence on entire groups of dissidents. The crowd ARE the suspects.
By the time you're hearing about it in the news they've already been doing it for years. I wouldn't dare set foot near any anti-Israel rally myself, suspecting the NYPD has been field-testing this for a while and activist NGOs like Canary Mission explicitly performing such recon and mapping themselves. All those DHS counter-terrorism grants weren't spent exclusively on MRAPs and bomb disposal robots. That money trickled down to a lot of interesting places.