Not understanding what this has to do with Android being open
"In order to obtain key mobile apps, including Google's own Search, Maps, and YouTube, manufacturers must agree to install all the apps Google specifies, with the prominence Google requires, including setting these apps as default where Google instructs," -
What has this to do with Android OS being open or not? Android OS is open and free (AOSP) for anyone to deploy however they want. If someone wants to add an app that is not part of the open Android OS such as YouTube, why can't Google demand a package deal? Issue will be if they make it such that for the open Android OS to work you need a specific Google service and to use that specific service Google in turn demands the above package deal. Considering what I had to do every time I flash AOSP or derived ROMs, that does not seem to be the case. So basically, the way I see it, anyone is free to use Android OS with whichever apps they want but if they want to use Google Apps, Google demands something. In that case, OS Market share (80% or 97%) does not matter.
Now, considering Google Apps only, sure Google is leveraging Search App to push other Apps. But their search market share is less than 70% and is not a monopoly.
"... from installing just (say) YouTube, but not Google Maps, if the manufacturer so chooses?" Edelman said in an email. "Or from installing Google Play and Google Maps, but DuckDuckGo for search?"
As long as Google is not having a monopoly in any of those App domains and does not make it impossible to use alternatives in open Android OS, there is no standing to demand that. If anyone decides to pre-package a Google App, that is more as a selling a point rather than a mandatory need. In which case, Google can do as it wishes.
What community should be worried about and keep an eye on is, if Google makes it impossible to use Android OS without specific Google Apps/Services.