You still have to grab the dependencies before running make, some of which you'll grab from apt/yum/chocolatey/macports, some you'll need to compile manually and put in a platform-dependent location, ...
Then you can run `make world`. Of course, BSD make is not completely compatible with GNU make...
OpenBSD and FreeBSD at least can compile themselves from /usr/src on a default install, fresh out of the box with zero additional packages.
"It can compile on a single platform from curated sources" is a very easy requirement to meet.
Ah yes, then there is the third big complexity. Some devs are on Mac, some windows, some Linux, and a few rare people on BSD.