To the "Touchpads are just touchscreens without the screen": yes and no. Touchpads are not touchscreens without screens. Touchpads don't operate on a 1:1 mapping where touchscreens do. If I touch the coordinates 1,1 on my touchpad, its a relative position to the current mouse location. If I touch 1,1 on a touchscreen, it's always the same position on the screen, regardless of where the pointer is located. They are both Human Interface Devices used to navigate, select and elements.
Yes, I know the Pixel isn't the only Touchscreen, that's why I said "for the Pixel and touchscreens."
I do agree that it is much easier to implement changes like what is recommended when it is in a largescale ecosystem. I personally don't see a need for a "create new tab" or "close current tab" gesture when there are shortcuts. I spend most of my time with my hands on the keyboard, not the touchpad.