In the IUnityGraphicsVulkan.h file, which provides the interface for creating Vulkan native plugins with Unity, there is a confusing comment relating to the kUnityVulkanRenderPass_EnsureInside enum value at line 96.
To further clarify the issue, consider the official Unity Vulkan native plugin example here: https://github.com/Unity-Technologies/NativeRenderingPlugin/blob/master/PluginSource/source/RenderAPI_Vulkan.cpp
On line 499 of this file, the native plugin event is configured to use kUnityVulkanRenderPass_EnsureInside.
The rendering function RenderAPI_Vulkan::DrawSimpleTriangles starting on line 637 submits a draw call to the command buffer, but it does not start a new render pass. It accesses the render pass provided by Unity in UnityVulkanRecordingState. Therefore, it's clear that UnityVulkanRecordingState::renderPass is non-null in this function, which would imply that a render pass is currently in progress. That is contrary to what the documentation seems to be saying.