Docs say Deploy Previews say preview will show result of merge, but it does not

That’s true! It took us some time to get here, but I get now that the issue is primarily about the docs. If you have a suggestion, I’d be happy to file an issue with our docs team. Maybe instead of

…building the site as it would be if the proposed changes were merged

I could suggest:

…building the site with the commits in your PR, before they have actually been merged

Does that seem like it’s on the right track?