SharePoint property panel allow us to change a Shared document set column

I have a document set content type named DS123, and it contains 2 custom columns D1 & D2 as follow:-

then i created a content type named "D" which contain a custom column named "D3":-

and define it inside the document set content type + i define the D1 as a shared column, as follow:-

now i created a document set folder based on the DS123 , then i added a document inside it based on the "D" content type. then i selected the document, where i will get those columns (D1 -the shared column- & D3), as follow:-

but the modification i do inside the D1 columns will not get applied, unlike the modification to the D3 column.. so what is the reason? is this that the D1 is a shared column from the document set? if this is the case, then how we can disable the field inside the property panel?

Thanks