Might I point out that the quote has two parts to it:
Across the fleet, the V-22 generally meets reliability and maintainability requirements"
considers fleet wide data which is probably similar to the numbers from the early 2011 articles.
Still, the V-22 in its most recent testing was available only 53 percent of the time it was required
considers data from a few, maybe even one aircraft. Was the non availability from mechanical issues, instrumentation, weather (did it have test instrumentation that made it a dry aircraft?), issuse with the new software, etc. There are many reasons why a test aircraft may not be available when a fleet aircraft would be. There is not enough information in the article to draw a conclusion either way. To do so is pure speculation.