Missing Default Attribute in the API response for certain categories

[Stanislav Mykhailenko]

We at Sellbery are developing updates to our application

The documentation we are referring to:

https://www.etsy.com/developers/documentation/reference/listing

Attribute Name: «Materials» is a default attribute.
Etsy also has Materials in Category Specific attributes. Example:

1. Case material (Material multi)
2. Material (Plumbing material)
3. Material (Material)
4. Material (Material multi)
5. Material (General material)
6. Handle material (Handle material)
7. Material (Sink material)
8. Material (Watch band material)
9. Surface (Surface material)

When Category Specific «Material» attribute is used:

1. «Default» Materials attribute still exists in the Admin interface of the product
2. Values of the «Default» Materials attribute are missing in the JSON
3. The most frustrating thing - there is «Gemstone» attribute for certain categories like Jewelry > Rings > Wedding & Engagement > Engagement Rings.

When we receive JSON we can see Materials and Gemstone attributes both for:
https://openapi.etsy.com/v2/listings/:ID/attributes 

{

"property_id": 148789511893,

"property_name": "Material multi",

"scale_id": null,

"scale_name": null,

"value_ids": [

83,

55,

68,

71,

98

],

"values": [

"Ceramic",

"Aluminum",

"Brass",

"Bronze",

"Copper"

]

},

{

"property_id": 102868018123,

"property_name": "Gemstone type",

"scale_id": null,

"scale_name": null,

"value_ids": [

1060

],

"values": [

"Diamond"

]

}

https://openapi.etsy.com/v2/listings/:ID

"materials": [

"Ceramic",

"Aluminum",

"Brass",

"Bronze",

"Copper",

"Diamond"

],

NOTE that Gemstone attribute was added to the «Materials». But values of the «Default» Material attribute were COMPLETELY ignored.

Question
Is there any documentation that can explain this behavior and any other attribute combinations that can behave the same way?