db.serverStatus().catalogStats returns a summary of the collections and views in the system as follows:

> db.serverStatus().catalogStats
{
  collections: 2,
  capped: 1,
  clustered: 0,
  timeseries: 1,
  views: 0,
  internalCollections: 5,
  internalViews: 0,
  csfle: 0,
  queryableEncryption: 0
} 

Legacy 'viewful' timeseries collection increment timeseries (due to the view) and internalCollections field (due to the system.buckets collection) but no other field.

Viewless timeseries collections should only increment timeseries but no other field.

Notably they should not increment collections nor clustered, both to avoid a breaking change and because they are not shown as clustered collections in listCollections.