Are DataPageHeaderV2.num_nulls and Statistics.null_count redundant?

[Antoine Pitrou]

Hello,

It seems a V2 data page can have its number of nulls recorded in two
adjacent locations:
1. the `num_nulls` field in `DataPageHeaderV2`
2. the `null_count` field in `DataPageHeaderV2.statistics`

Is this interpretation right? Or do those two fields actually have
different semantics.

Regards

Antoine.