Thank you for the link.
From Preloading Updates question - #5 by OrsoBruno i understand openSUSE-repos-Tumbleweed also modified zypper to download in parallel. From my limited understanding, that does not seem like a task related to repositories only, but a change in the configuration of zypper?
Is there a reason why openSUSE-repos-Tumbleweed is not installed by default and hence I should uninstall it again from my desktop?
My concern is: Would I ever have gotten the parallel download feature without having openSUSE-repos-Tumbleweed installed (other than messing with configurations files manually)?