This change prevents users from creating a view on top of a time-series bucket collection namespace (prefixed with "system.buckets"). We never intended to support this behavior, and we had some associated bugs. Users are advised to drop any such views before upgrading to a 6.1+ binary. If they do not, they may need to drop all views for the affected database after upgrade.

Description of Linked Ticket

I thing the intention behind hiding custom views on time series collections was to disallow manual creation of those. For now you can create them and they behave oddly.