"The resulting reconstructions are validated with rigorous statistical analysis, and not used unless statistically valid. There has never been any manipulation of data to skew results.

It is hard to say Tree Ring data is both curated for validity and say there "has never been any manipulation of data" at the same time.

Is the complete data set preserved (all data accepted and data rejection alike) in these data sets?  Otherwise, your assertion is hard to justify.

We know that some tree ring data was purposely tossed, wihere some of which was only by chance recovered when one of the authors died, and his data from his estate was published by his university.