Promoted to core in Vulkan 1.2

On some implementations, setting the VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT on VkImage creation can cause access to that VkImage to perform worse than an equivalent VkImage created without VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT because the implementation does not know what VkImageView formats will be paired with the VkImage. This may force the implementation to disable (VkImageView) format-specific optimizations such as lossless image compression. If the VkImageFormatListCreateInfo struct used to explicitly list the VkImageView formats the VkImage may be paired with, the implementation may be able to enable format-specific optimization in additional cases.

If the application is not using the VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT to create images, then there is no need to be concerned with this extension.