That response repeats the party line about Android being "open", but part of the narrative that MG and Gruber keep pointing out is that it's just not true. The carriers lock things down and fill your phone up with unwanted junk far more than Apple does.
"Open" means open for the carriers to do what they want, not for you to do what you want.
I don't believe there are any carriers any more that stop the user installing from non-market sources. Many offer ways to unlock the boot loader so you can completely control the device. You can always buy a Nexus device. These are all forms of openness (although I would tend to call it "freedom" since that more accurately describes it).
> it's just not true
As I point out above, it's very true. What I think iOS advocates point out is that it's not practical: no regular consumer uses these things in practice (although the Amazon Appstore might be an example). What matters in practice is how the device comes out of the box because 99% of people just use it like that. I acknowledge this, which is why I say it's an intangible feature of Android. You only value it and benefit from it indirectly. I guess my only point is, if the Sieglers and Gruber's of the world want to claim intangible things as assets for iOS then they should be acknowledged for Android too.
Even if 99% of consumers use Android devices just as they come out of the box, the existence of escape hatches is still an important check against carriers, manufacturers and even Google.
For instance, nothing like Apple's in-app purchase crackdown could have happened on Android. The big players (Amazon, B&N, Netflix, Hulu, ...) would have just taken their apps out of the Android Market, clearly communicated to their customers where the apps were now and moved on.
Similarly, as I understand it, it was the Android hacking / ROM development community that discovered Carrier IQ in the first place, specifically because they are taking apart the software on their phones and trying to understand every bit of it. Personally, I find the contrast with the iOS jailbreaking community quite instructive. Once they knew there was something to look for, they found the Carrier IQ traces in iOS quickly enough. Nevertheless, without the initial pointer, they didn't notice anything..
"Open" means open for the carriers to do what they want, not for you to do what you want.