As time goes by we realize more and more that trees aren't usually good pro and aren't good or appropriate for anchors ("usually," exceptions exist to most rules, and a huge and healthy tree might be an adequate anchor for a very rarely done route).
But it's important to balance this realization against the ethic of not adding bolts to routes established by other people (an ethic that has very likely saved the element of adventure in climbing as a sport - a different and longer discussion, not for this thread).
Here, the balancing isn't even close. No-one knows who did the FA of this 30 foot high route. No-one actually knows for sure that anyone did any more than place a bolt in that short streak. And no-one knows what "they" did or didn't do for any necessary top anchor (the damn bolt looks like it could be older than the three-inch diameter tree!). I've rapped off that tree several times and also wondered if it would hold. And even "once-in-a-while" raps can't be good for its health.
I know of no person who would object to adding a quality anchor there. I am, however, going to be making some phone calls on another Pinnacles subject, this week, to known and concerned Pinns climbers who are not on this site. I'll ask their thoughts (mostly as a courtesy?) on this issue too and report back any negative comments (don't expect any report back, but give it a week or two just in case?).
And thanks Gavin for being willing to do the work.