It's a bug currently, report then here:
I had a similar problem and this was fixed in the latest OTA.
I had to wipe cache in recovery and cache for netflix and the drm info app to see it though. Try the same.
Widevine 13 issue, kindly try this,
Go to google play store>settings>biometric authentication. If the toggle is disabled, just enable it. If prompted to enter password, enter it.
Reboot the phone once and check the widevine status using the DRM info app from the play store. Probably check back in some hours if not immediate
It should corne back to L1.
If Netflix is still showing SD, go to Netflix app info, clear cache, data and uninstall updates. Reboot, install updates and check out the playback specification.
OxygenOS 11 Open Beta 1 for the OnePlus 7 and OnePlus 7 Pro
by Abdul B., 2021-01-20