When one openes the Print dialog, the "Print" button is the default, that is from keyboard, if one presses "ENTER", it will print. 
The main action being print, it must always be the default button. 

1) if you press "Properties" for the selected printer, the "Print" button becomes a regular button and you have to click it, or navigate to it with the keyboard. 
It this case, changing window tabs returns the state of default button to the "Print" button.
2) if you press "Help", the "Print" button remains the default.
3) if you press left/right buttons to navigate pages in the preview, the left/right button becomes the default. In this case, changing tabs does not return the default state to the "Print" button, but the left/right button in the preview area retains it's default status.