I'm not sure if you understood it correctly (or if I even expressed it correctly). The operations are of course executed sequentially, always (that's how our package managers work). But they can be *scheduled* concurrently, i.e. you can install GIMP, and before it is downloaded and installed, you can also schedule installation of Inkscape. I think this is not an unusual use case, to schedule several operations at once. E.g. I just installed a new system and want to install my favorite applications. Or I decided that I want to play a different game, so I hit Install on OpenArena and also click Remove on SuperTuxKart.

Is this really what you are against, or have you understood it differently? I can try to phrase it better.

See my response above. Imagine that we'd ensure only the first dnf operation works correctly, but any later one can blow up. Why would we want to allow that with a graphical package manager?