Instead of Steam forcing any disputes with them to go through an “impartial” 3rd party company they choose and pay for to oversee and rule on disputes, they are saying that disputes must go through the courts.
Basically forced arbitration has always been seen as anti-consumer and unfair because the company is paying for the arbitration and is thus considered more likely to be found in favor of. Steam is doing the opposite and as such this is seen as pro-consumer and a good thing