Of course it doesn’t read the future 
. The fade out on NodeBB seems to be about 200ms. If the page takes longer to load, then you’ll contemplate a blank screen.
And yes you’re right, the idea is basically replacing the spinner by a fixed duration fade out. 
If the loading time is faster than the fade out, then the fading should be interrupted to let the new content to be displayed.
Programming isn’t my primary skill and I don’t know how Discourse works, I’m not sure I’ll figure out, but that’s worth to take look.
Thanks for your advice and suggestions!