My guess would be if you are seeing 404, you are using a bookmark to a special/direct link within the domain. Have you tried www,yourdomainnamehere.com ? THAT is what would see the "technical difficulties" error page that was modified.
Well I see the problem now.
I was not using a bookmark, however:
I find that if I type in anything not in the root directory, I get the 404 - eg, hostname/folder/index.html.
But it is true, if I just type in the hostname, or hostname/index.html I will get the "SORRY" page.
However, this message is no more informative or less foreboding to users than the 404 page was:
"If you are the owner of this website, please contact your hosting provider: firstname.lastname@example.org"
I thought there was going to be something like "We know there is a problem, and we're working on it."