This really deserves an explanation in the code.
Note also that what makes this work is not so much that the load src is uniform (and hence "real") but that it's constant. In fact, more broadly, we can safely copy-prop an object load *if* the load var doesn't change between the prior load and this resource instruction. We don't have the infrastructure right now to do that with all variables (we could if we wanted to, but it's probably not worthwhile—doing it with uniforms alone should probably be enough?)
We could, hence, check for HLSL_MODIFIER_CONST on the variable instead of is_uniform. That would, notably, require that we create uniforms with a constant data type, which we don't currently. I dunno if it's worth changing that yet, but there is a bit of a "least surprise" element here.