Setting a subcategory in a UPROPERTY does not display properly in associated blueprint's Details tab

When using the "|" operator to separate "Category | Subcategory" inside a UPROPERTY, a blueprint based on the class will show Category | Subcategory AS the category name instead of listing a category containing a subcategory.

Extra info:
The Category / Subcategory appear correctly inside the right-click menu in blueprints.

1. Open UE4 Editor (any project)
2. Add code to project based on actor (MyActor)
3. In MyActor.h, add the following:

   UPROPERTY(BlueprintReadOnly, EditDefaultsOnly, Category="Creature|Thermal")
   		float IgnitionTemp = 200;
   

4. Compile
5. In the editor, create a blueprint based on MyActor (MyActorBP)

Result:
When MyActorBP is opened, category for IgnitionTemp is shown as "Creature|Thermal"

Expected:
Details panel shows Creature as the category and Thermal as a subcategory where IgnitionTemp exists

UPROPERTY Category doesn't apply subcategories