@michael-petitclerc I got it now:
Although the settings are the same, various settings get precedence either in Quality tab, or in Material tab.
The only thing that is still confusing is that as is now, without testing, the user can't tell which is the higher precedence setting.
layer thickness - if set different in the two panes, the setting in Quality will take precendece
speed - again, if set different in the two panes, this time the Material will take precedence.
I could not tell the above without actually trying it, which I believe is a flaw in design.
Plus, why both settings would have the same set of parameters? What's the purpose behind that?