When the touchpad is set to emulate a mouse scroll wheel while using a circular gesture, swiping clockwise is scroll down and swiping counter clockwise is scroll up. Of course, you can change this if you want:
Steam>Settings>Controller>Pair and Manage>Desktop Layout>Edit>Edit Layout>Trackpads>Left Trackpad Behaviour>[gear icon]>Invert Swipe Direction
Or just swap the "Clockwise Command" and the "Counter Clockwise Command" under Steam>Settings>Controller>Pair and Manage>Desktop Layout>Edit>Edit Layout>Trackpads>Left Trackpad Behaviour
But regardless of the fact that it can be changed, there must be some logic to why the Steam Deck touchpad behaves that way by default, right? Help me make sense of why some dev team at Valve decided that the default should be "clockwise=down" despite these other common scenarios in which "clockwise=up".
That logic does make sense with the default layout of the left touchpad being used as the scroll wheel, considering that the element that is being scrolled (the screen) is on the right side of the element that is controlling the scrolling (the left touchpad). If someone were to swap the touchpads (so that the left controls the pointer and the right controls scrolling), they would probably also want to invert scroll direction if they want to follow that cogwheel logic.