OnePlus is really struggling to keep its smartphone portfolio updated. Even when updates arrive, they more often than not introduce bugs — the Android 12 beta bricked OnePlus 9 handsets, for example. So, I'd understand if you're skeptical about this, but OnePlus has rolled out the May security patch for the OnePlus Nord N100, 6, and 6T.
The changelog for all three devices is pretty tiny, and the only other entry is that of bug fixes and improved system stability. The company doesn't address what exactly has been fixed, but we just hope the update doesn't introduce any new problems.
All three phones are due to receive the Android 11 update — the last official OS version for all of them — but users will have to wait a while. The OnePlus 6 and 6T will only get the Open Beta sometime in August, meaning the stable update will roll out closer to the end of 2021. However, if you're a tinkerer, you might be happy to learn that LineageOS does have Android 11 ROMs for both these devices.
OxygenOS 10.3.11 for the OnePlus 6 and 6T and OxygenOS 10.5.8 (10.5.10 for EU) for the Nord have already begun to roll out. If you haven't received your update yet and are eager to try it out, you might want to check the unofficial Oxygen Updater app — that will help you get the latest OTA.