Your last point first…
Contributors here are all end-users, just like yourself. We can’t change or influence anything - except by providing feedback to Apple via their Product Feedback portal. Also, be aware that beyond the site Moderations, here present to ensure that we all follow the Terms of Use that govern our participation within the Support Communities, Apple do not actively monitor these forums.
Apple invite submission of constructive comments and feature requests for iPad and iPadOS here:
Feedback - iPad - Apple
As for location of the multitasking button, we can only speculate as to the decision to place the button at top centre. You can be sure, however, that one persons “ideal” will be another’s bugbear; the location that works for you - and your chosen Apps - will impact somebody else. As is, Apple’s design interface places the button in one consistent location; image the confusion that would occur if the button location were to change for each App…?
As for the issue with Safari, it is unfortunate that the multitasking button has close proximity to the centre of the URL (address) bar. It is possible to tap the centre of the address bar without triggering the adjacent button - but only if you are very accurate in placement of your fingertip. It is, as I have attempted to outline, far simpler to develop the habit of tapping anywhere else than dead-centre. Habits are formed; your’s is currently to tap dead centre; you will rapidly adjust with just a little initial conscious effort to change established behaviour.
Your doctoral research is no doubt very well informed and admirable in its scope. Whilst having no intention of engaging in deep discussion of the topic, your research will no doubt have encountered human factors and established behaviours - and people’s fundamental resistance to change. I doubt, however, that it will have fully encompassed User Interface Design in context of touch-UI. To strike a direct and hopefully useful analogy, imagine the consequent usability issues and chaos that might occur if all users were to design their own keyboard layout. With QWERTY (predominately English speaking), AZERTY (French, Belgian), Dvorak (alternative English) and others, you have an internationally recognised “standard” keyboard layout (i.e., Interface Design).