Personally, I'm not an android, or open source, advocate. I don't use it at the moment and I wouldn't necessarily recommend it to someone else. All the phone oses I have have used are flawed to some extent and picking one is a matter of deciding which flaws you can tolerate or not notice.
Gruber doesn't care about openness either, he uses an iPhone. His argument is is simply a way to bash android without addressing anything that is substantive to most people.
Last month he was trolling that android wasn't open because motorola hadn't provided a froyo update to an older phone, completely ignoring the fact that the comunity had already provided multiple updates.
Next month he will be complaining that android isn't open because google hasn't provided the source to something else.
To most people, it doesn't matter if android is 65% or 70% open. What matters is how well it meets their needs. If openness helps meet those needs then it's important, if it doesn't then it's irrelevant.
Finally, if Gruber was interested in openness, he would allow comments on his blog. Without that, he is just a troll with a pulpit.