Its grandstanding and posturing.

But there is actually a good argument. Someone who the DOJ have decided wasn't worth the hassle to properly investigate might still be identified and reported by a co-worker or neighbor. Which then begins to force the DOJ's hand (they are still cops so they might ignore it but...). I personally think everyone who crowded outside the building deserves to be locked up, but I can see an argument that only people who entered the building or who actively caused damage should be charged.

Because yes, facial recognition and DMV databases are already a thing. But, much like with a red light ticket, a decent lawyer can work wonders to argue out "a robot claims that I commit a crime". Whereas having a human in the loop removes that gotcha. Hell, if my cousin is any indication, you don't even need a lawyer to argue against a red light camera or an automated speed trap and just need to care enough to show up to the courthouse for a few hours.

Also, regardless, this is indeed (attempted) obstruction of justice to protect insurrectionists.

any little suspect from small time crime gets their face plastered all over local news

Only if they're black or hispanic. There's a narrative to push, don't you know.