A flag is needed to suppress sending the action to the browser and only to update state of the pointer

In chapter 17. Actions, section 17.3 Processing Actions Requests:

When required to process a pointer up or pointer down action with arguments action item, and action, a remote end must run the following steps:

Let button be the result of getting the property button from action item.
If button is not an Integer greater than or equal to 0 return error with error code invalid argument.
Set the button property of action to button.
Return success with data null.

For some of the pointertypes that don't support hover (like current touch screen devices and some styluses) the first action that they inject is indeed a pointerdown and no pointermove before them. So similar to the pointermove we need x,y, and origin for pointerdown as well.

Start with the WebDriver specification's section 17.3, “Processing Actions Requests,” and compare the pointerdown steps with the pointermove processing described nearby. Determine the required x, y, and origin information for pointerdown actions, then update the specification so the requested behavior is explicit and verify the surrounding action-processing text remains consistent.