[Bug] [Vulkan 1.2] Fragment shader output as vec2 requires strange color write mask to work

Hi, this is my first bug report here, so if any more information is required please let me know. I have a fragment shader that writes to some color attachments. And one of them has format R8G8_UNORM. I declared it as a vec2 in my fragment shader. Now when setting the vk::PipelineColorBlendAttachmentState::colorWriteMask for that attachment to vk::ColorComponentFlagBits::eR | vk::ColorComponentFlagBits::eG (as its logically supposed to be since I only have a red and a green channel), that color attachment doesn’t get written to. If I set it to vk::ColorComponentFlagBits::eR | vk::ColorComponentFlagBits::eG | vk::ColorComponentFlagBits::eB | vk::ColorComponentFlagBits::eA; everything works fine. Could this be a driver bug?