Well they have to abide by the arbitration and any good arbitrator will put a good faith clause in the agreement.

Is it hard for a big tech company to find a bar arbitrator that won't require that in the initial customer agreement?

If they did that, then there would be no incentive for customers to choose arbitration over filing a dispute with their credit card.

Arbitration is likely even more expensive than a dispute.

More choice of arbitration firms than credit card arbitration firms (for them, not you!)

Doesn't help if each arbitration case costs a low triple-digit amount in arbitration fees + creates an expensive case in the legal department.

The arbitration is painful because of the costs (financial and staffing/handling) of the process, not the outcome.

At the individual dispute level but in the long run arbitration means you don't lose your risk level which will almost always cost you a lot more than whatever the actual arbitration/credit disputes cost.

I suspect (but may be wrong, I don't know how trigger-happy the risk level changes are) the absolute number of events needed to trigger a risk level loss at the scale of Twilio would also represent a catastrophic number of arbitration cases.