He shows the pads moving toward the disk looking thru a hole from the back.
 - Barrel adjuster is just for taking out cable slack, not for moving the pads (so pads only start to move

ChatGPT: Lever pull translates directly to piston movement. There is no "free movement" of the caliper arm without moving the piston. So if you were doing it wrong, you could have a big gap in the pads, then tighten the cable so the pad starts out moved part way in. And subsequent cable movement puts the brakes on. the resting place determined by the lever.

 - put in lowest gear, drop the wheel
 - turn by hand, stuck so use T25
 - take pads all the way out
 - remove brake pad with needle nose
 - inspect thickness of pad
 - pads are marked L and R
 - he adjusts the inner one to take out too large a space
 - rotor doesn't deflect

My actual experience is that Avid BB7 is incredibly difficult to seat properly. So eventually I switched to TRP Spyre.