On the "No wiki found" error page for a nonexistent *.wiki.local.wmftest.net vhost subdomain, the main devwiki is linked to as "127.0.0.1:8080", which will not work under many circumstances. We cannot assume that the devwiki is the server's default site.
The tricky part here is that the main wiki doesn't really know what its FQDN is. The MultiWiki boot loader checks the hostname for the request and if it can't figure out a wiki attached to the name it give the pretty error screen. The values in the error screen come from the $wgCanonicalServer values in settings.d/wikis/*/wgConf.php. The $wgCanonicalServer for the default wiki is http://127.0.0.1:8080 (modulo the port number).
Yesterday I installed MediaWiki-Vagrant from https://mediawiki-vagrant-image.wmflabs.org/wiki/Main_Page and enabled and provisioned Flow. The "No wiki found" error page for a nonexistent *.wiki.local.wmftest.net gives a list of available wikis in the farm. On top is devwiki, which links to http://dev.wiki.local.wmftest.net:8080/ and not to an IP address. Looks like resolved to me.