Pop!_OS uses COSMIC (a modified GNOME), not KDE.
Linux Mint uses Cinnamon (a modified GNOME 3) or MATE (a modified GNOME 2), not KDE.
The answer to "why not Debian" is that I try to install Debian first every time, but if it doesn't work for whatever reason I grab Kubuntu instead of trying to troubleshoot it. 3 of the 4 desktop computers I've tried to install Linux on lately ended up with Kubuntu instead of Debian.
(For my personal desktop that tends to have a bleeding-edge graphics card at the time of building/installing, that's understandable. For the other computers, for other members of my family who don't need the latest and greatest, Debian's failure to support several-year-old hardware -- at least in the installation environment, without fiddling -- was less forgivable.)

To be fair, it's plausible. They might not have wanted a home inspector writing up "low water pressure" as a potential problem. 'Course, the inspector might write "water splashes out of the sink" as a problem instead, but that at least is more straightforward to solve, rather than being possibly indicative of a bigger hidden problem.