Material instance UI doesn't show correct parameter preview for logic in a material function

The Material Instance UI doesn't show the correct parameter values when the logic is moved from the material graph into a material function used in that material graph.

Example setup showing the wrong color (green) is visible in the Material Instance UI where it should be red.  
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1. Create a material graph
2. Add a static switch and plug a static bool parameter into it.
3. In the static bool parameter's details, check "Dynamic Branch".
4. Plug two color parameters into the static switch and connect the output to the Base Color of the Material.
5. Create a material instance and toggle the bool - note the UI hiding and showing the relevant params, the UI color switches from green to red depending on the state of the bool parameter.
6. Move the color parameters and switch into a function, add a function input parameter of type "bool" (NOT static bool).
7. Plug the bool param at the root of your material into the function's input and plug the function's output into the material Base Color
8. Save the material and material function
9. Back in a material instance, toggle the bool.

Expected

The UI color for changes like it did before the logic was moved into a function

Actual

The UI color no longer changes