Removing the title bar tap behavior has it merits. But why can’t this be an adjustable option? I read a lot of rather short papers and being able to quickly jump to the top to get references was a blessing. I therefore propose a three-way switch:
(1) title bar tap is active
(2) title bar tap is not active
(3) title bar tap is adapative
Explanation to (3): Since you grab the reading position for every doc anyway, the title bar tap would bring you back to the top from any position of the document (with caching the previous position) and right back to that position of you tap it again without scrolling inbetween. Best for accidental and intentional taps. Also suitable as stand-alone solution without switchable settings.