ClickCallback/forEachMatchingRecord not getting data in every case
If there are more than one attribute in either the row or column attribute box then pivotData.forEachMatchingRecord is not returning any values for the marginal totals including the grand total. Using the default data set on the demo at https://react-pivottable.js.org/
In this case below for 2 attributes on the side attribute box, the bottom totals do not have data in the ClickCallback/forEachMatchingRecord
The circled cell was clicked in the image below

This works properly for pivottable.js indicating perhaps the version of pivottable.js that was the basis for react pivottable is not the latest,
If this works in PivotTable.js and not here, then I agree it's a bug, and I'd happily accept a PR that fixes it :)