Are home screen icons restored after reinstalling a Nexus device? I reinstalled my Nexus 5 from scratch, erasing everything. 

I had Google account sync on. After signing in, all my apps came back in a matter of minutes.

But home screen icons, widgets, folders did not come back, even after a couple of hours. Should I keep waiting for them? Is there any hope? My homescreen background appeared out of nowhere an hour later. Maybe that's a sign? 

There is absolutely no progress of restore operation whatsoever unlike iOS devices, which show ghosted icons for apps to be restored. When is it over? When can I assume what's gone is gone?

I will stop waiting and start working on hours of drag'n'drop sweetness if it doesn't support restoring of home screen icons. It's ridiculous but not more than staring at an empty home screen and praying. Is there any place that I can debug this issue? Or re-trigger, force, whatever?
Assuming you are using the stock Google launcher...

In my experience, no, they are not restored automatically. Only the wallpaper is restored.

That being said, if you had made a backup using Titanium Backup or something similar this would be able to restore your home screen design. Just reinstall your apps first and then restore the backup.