Senator Francis Tolentino emphasized Senate Rules on invetigation in aid of legislation and that respect should be observed.
There are two instances wherein the resource person cant be compelled to answer: 1. If the resource person cites his right vs self incrimation 2. that the topic of inquiry as often are, especially in the Congressinal hearing, ir outside the concern of the inquiry. Thus may be citing for contempt or judging that a resource person under these rules are out of order.
May be these reminders made the Duterte hearing "tame" and that it was an invasion by Duterte. That there was too much respect.