OnePlus explains that depending on when a phone launches, they can include the out of box software as one of the updates. For the OnePlus 13, as an example, the Android 15 is included as the first Android OS update and only plan to provide Android 16, 17, and 18 following that. So no Android 19 update would be provided.

OnePlus tells that this has always been their update policy, which apparently not many people understood correctly. They believe that releasing new software and placing it on a phone at launch, followed by a year of support on that OS version, counts as an update.