There seems no reason to think this is a bug. Apple say:
Apple only displays data from users who agreed to share their diagnostics and usage information — no personally identifiable customer information is included.
Data is aggregated and gathered from the following devices:
- iOS 11 or later
- macOS Catalina
- iTunes 12.7 or later
Note: Date range data begins at 12:00 a.m. and ends at 11:59 p.m. (UTC). Diagnostics and usage information might be delayed by up to 72 hours.
Minimum thresholds
If your show displays a “Not Enough Data” message in Podcast Analytics this means your show has not met the following data thresholds for the time frame specified:
- At least five unique devices must play content from your show.
- Each unique device must play the content for at least five seconds.
https://itunespartner.apple.com/podcasts/articles/data-requirements-3072