I watched the summer riots on youtube live streams, I don't recall the FBI using this technique for the tens of thousands of man-hours spent looting, burning and rioting in Portland, LA, Seattle, Minneapolis, Chicago, NYC or Atlanta.
I don't think its the FBI's job to figure out who smashed up a Target or looted a Footlocker.
Its definitely the FBI's job to figure out who breached a federal building, let alone the seat of our legislative branch during an active session.
That being said... the FBI, DOJ, DHS, and state agencies definitely do shady stuff and track people via their devices at protests. I'm remembering surveillance planes over Baltimore that were traced back to feds.
Your linked article is about a company data-mining Twitter. TFA we are discussing is about the FBI getting location data from phones. These are two very different things...
Your point was clearly the broader law-enforcement tracking, you sought to draw a comparison between the two events to ask why one had been an infosec focus of law enforcement.
