Except they cannot, Chromium (or is it Blink?) changes too frequently to reliably code for one version and expect backward compatibility of future releases. Electron versions could be shared libraries... except again BC breaking releases proliferate.
Why can't it be based of Chrome's version number? If you know the version number at the time of release then you can say only use the same runtime if there's only a revision version difference, else you can use it's own run time. That packaged with auto-updates for the app to that developers can push updated builds every month or so should be fine.
Except they chose not to, preferring to allow for frequent breaking changes. This makes it easier for devs to make these rapid changes with all the cost/overhead payed by you.
