While I think the skepticism towards the 100% coverage effectiveness is valid, I'm not sure how to make meaningful conclusions from the number of bugs per product reported by that analysis (the analysis itself is certainly a really good job).
MySQL's bug tracker for example is huge (but I don't imply anything negative). During my last two work days, I've experienced two bugs, one of whom was new and caused a server crash with a SELECT. A couple of months ago I've found another server-crashing SELECT, which was also a new bug. I've filed a number of other bugs in the order of the dozens, over the last years.
There is a significant number of bugs reported in the SQLite fulltext functionality (if I understand "FTS" correctly). I don't see any in the MySQL section, and I'm perplexed, since the MySQL FT implementation is (relatively) poor, and I'd be surprised if an in-depth exam wouldn't find any bug.
Possibly, they've dedicated a significant amount of resources specifically to SQLite, either in terms of time spent testing or time spent tooling specific to it.