Exactly this. Kde's graphical application store actually has a warning on arch, since pacman can be even more problematic when it comes to abstraction layers like GUI's.
At this point, rpm's and deb packages can be auto updated through their relevant package managers. And it looks like gnome software is attempting to try to get user packages installed via flatpak entirely.
K = kilobytes.
45347740 bytes is 43.247 megabytes. That is to say, the entire install of filelight is only 43 megabytes.
KDE packages have many dependencies, which cause the packages themselves to be extremely tiny. By sharing a ton of code via libraries, they save a lot of space.