IE
"Need a Mac because you're wanting to explore iOS development? Get the Mac mini and continue to use the keyboard/mouse/display that you've already got on your desk. It's no longer the affordable way into the macOS environment that it once was, but it's the best thing Apple really has to offer."
"Apple's refusal to build, y'know, a regular desktop computer means that the mini often ends up being the best option if you really are committed to using macOS."
etc
I've own/owned 5 or 6 mac mini's at this point (including the 2018)
At this point, i buy them to shove them in a closet somewhere. Size is not a factor in that.
It's big enough at this point (compared to NUC's, etc) that it has no meaningful size advantage.
As a server, you'd want some different tradeoffs. As a desktop, the only reason you'd use it is, as the author says - you don't have a lot of options in what you can use for MacOS and this checks some boxes the other option doesn't.
It'll probably be the last computer i buy from apple to set up for others - MacOS isn't as bulletproof as it used to be.
For the second time, I had to debug obscure apple bugs for my parents over thanksgiving - which is why i set them up with a mac mini in the first place - to stop having to deal with this on windows or linux.