A clue that someone has had media training. It is, apparently, rude to point. But people feel a natural inclination to do so when accusing each other.
The media trainers seem to teach people to tuck their index finger in… but that leaves the thumb resting on the tucked finger.
The hand still jabs towards the accused but it isn’t, in the hair splitting terms so beloved of politicians, technically pointing. In the same way a blowjob is not “sexual relations”.
Watch Question Time… you will see this all the time. For the advanced observer you can find out how angry the pointer is by how far the thumb protrudes.