Legal to use single-sampled attachments for multi-sampled pipelines?

I have a shader which uses two color attachments, one for regular colors, and one for especially bright colors (used for a bloom effect).
When using MSAA, I don’t really need the bloom-texture to be multi-sampled, since it’s blurred later on anyway and a single-sample texture would save me the resolve-operation (as well as GPU memory).
So that means I would use a multi-sampled color attachment (for the ‘regular’ colors) and a single-sampled attachment (bloom) in the same shader pipeline, is that legal? I can’t find anything about that in the specification.
I can set a sample count in the VkPipelineMultisampleStateCreateInfo-struct for the shader pipeline, does that mean all attachments HAVE to have that same sample count?
This is what the specification says:

rasterizationSamples is a VkSampleCountFlagBits specifying the number of samples per pixel
used in rasterization.

I don’t see any limitations anywhere, but maybe I’m missing something.

Legal to use single-sampled attachments for multi-sampled pipelines?

No.

This is a property of the subpass, not the pipeline. So it’s impossible for a supbass to have color attachments with different sample counts.