Also there are subtle differences in platforms which means you actually need to test. Simple examples are menu differences (no app menu on windows). Forking external command line program differences. Application data differences etc. (maybe someone will make the electron cross platform CI tester?)
If they are planning to package this program for Windows, Linux, Others then good, nice release, but I would still criticize because they are using a technology that is supposed to be a tool to build cross-platform applications from the beginning, if they already have the HTML / JavaScript code for this, what is stopping them from packaging the Windows version for example? I don't see anything in the feature list that requires Mac specific hardware / tools.
If you're doing something graphically intensive, there's also always WebGL. At the current rate the browsers are going, I expect the case to do native apps to be shrinking. Stuff is already running at 60 fps in the browser these days and most people can't tell the difference past 60 fps, and the benefit of getting access to the javascript/HTML web ecosystem outweighs any other points for most apps.