Major Description
Based on the issue you've uncovered (that stats must be updated completely for a region), there's a bit of follow on work needed if an ANALYZE is done on a tenant-specific table. This case will be optimized to only scan and analyze the current tenant's data, however we have to make sure that the entire region(s) containing that tenant's data is scanned (or we'll end up replacing the stats for that region with just the one we calculated for that tenant).
We should be able to do that based on ScanUtil.isAnalyzeTable(scan) being true in DefaultParallelIteratorRegionSplitter and/or ParallelIterators.