According to the linked thread it seems there is a lack of supply for used for 777 parts (as you'd expect). Now that planes are at the decade mark I could see how the demand for parts would be on the rise. If the only source is new Boeing parts then it's entirely possible that even a perfecly good 777 could be more valuable as parts than as a working airframe. So why not recycle it?
It could be that there is nothing wrong with this plane and is only being scrapped because of the high parts value.
You are probably right. I think combine this with the fact that development of the model (and others) has happened quite quickly in the past decade or so (this being a bog standard 777, not an ER etc...), so airliners are having a shorter life with their original operators.