Allow arrays sized with specialization constants in Buffer variables?

[If I understand the spec correctly](https://docs.vulkan.org/spec/latest/appendices/spirvenv.html#VUID-StandaloneSpirv-Function-04681), arrays sized with specialization constants cannot be used for Buffer variables except for some input and output variables. That is a bit surprising, and means structures containing such arrays cannot be read or written from Uniform or StorageBuffer memory. For PhysicalStorageBuffer you could work around it by looking for the elements after the struct, but that complicates things. Is there any particular reason for this restriction?