It is clearly stated in doc/changelogs/4.7/CHANGELOG-4.6.0-to-4.7.0.txt
"Make sure the YUI3_config is used when loading YUI3 components"

One consequence of not complying to this Change note is that any custom implementation that includes a YUI().use(<module> on a site with [eZJScore] Packer=enabled , will have the <module> being loaded from yui.yahooapis.com, regardless of LoadFromCDN set value.

It took me sometime to first notice the note in the changelog. Until then I did not understood why, on my test environment, some yui modules were being loaded from external sources.

Wishing to make sure that my code was in compliance with eZ's main one, I grepped eZPROOT for YUI().use( . Found two relevant locations:
/extension/ezfind/design/standard/javascript/ezajaxsearch.js
/extension/ezflow/design/iphone/templates/pagelayout.tpl

Although I have not been able to reproduce the issue with eZFind, it's easy reproducible in eZFlow's iphone design.

steps to reproduce:

• Setup an eZPublish 4.7 with eZFlow
• Set [eJSCore] Packer=enabled | LoadFromCDN=false | PreferredLibrary=yui3
• Clear browser and eZ caches
• Access the home page in iphone siteaccess
• Verify that http://yui.yahooapis.com/combo is accessed to retrieve the required modules

This is a minor issue, nevertheless, I report it here to call everyone's attention to the note in changelog quoted above:
Make sure the YUI3_config is used when loading YUI3 components