OxygenOS is OnePlus' well-received skin for Android. The OEM runs a beta program for this software, by which users can access new features in advance and offer feedback on the same. Now, however, the company has announced that it will reduce the number of these builds released per month.
https://www.notebookcheck.net/OnePlus-halves-the-frequency-of-its-Open-and-Closed-Beta-programs-for-OxygenOS.469339.0.html
The reason is probably pure pragmatism. BBK has Oppo, Vivo, OnePlus, IQOO and Realme to maintain and they can't guarantee the same pace of updates for all their devices.