I think the author is confused between "tracking bugs" and "a bug tracking system". The former is a social process, and something that all projects do on some level. The latter is a piece of software, which may or may not help the project to do the former. The author even discovered the evidence for this, but missed the meaning: git's bug work happens on the mailing list, while mono's goes on in the tracker.
Don't confuse software with problems. That's how we get bad software.