UP printer reports don't contain page count info

When we query https://graph.microsoft.com/v1.0/reports/printUsageByPrinter we get lots of info but pageCount is always zero for all Universal Print printers. We've used other endpoints and it's always the same for both v1.0 and beta. We went to the portal and downloaded the report and it shows the same - plenty of jobs completed but zero pages listed as pageCount for all printers.

Has anybody else seen this and if so, can you explain and hopefully tell us what is needed to enable collection of this data? We need to be able to build usage reports and page count is sorta fundamental...

Thanks in advance -

Joe.