The implication is that in theory you could set VKD3D_SHADER_COMPILE_OPTION_FEATURE_WAVE_OPS with VKD3D_SHADER_SPIRV_ENVIRONMENT_VULKAN_1_0, but that wouldn't allow translation of sm6 waveops because we wouldn't be able to use SPIR-V 1.3.
Part of what I'm thinking is, from my interpretation of the spec, it's not actually legal for an implementation to expose all the flags we need for wave ops but not actually support 1.1 (and by extension SPIR-V 1.3). So adding anything about 1.1 is kind of redundant.
Having VKD3D_SHADER_SPIRV_ENVIRONMENT_VULKAN_1_1 makes sense for some measure of consistency; it's just not clear to me we need it.