Shadow banning was allowing certain people get away with way more policy violations than normal individuals that would of been banned outright and kicked off twitter almost immediately with a lot fewer violations. "Corporate propaganda" is what one ex employee called it. Like Traitor Trump “Between Jan. 6 and Jan. 8, Mr. Trump tweeted 140 separate violations of our policies and procedures before we ended up banning him.” Essentially "shadow banning" was many times just giving special privileges and allowances for violations of policy that the normal person would not get.