Applying delay to logic in interface using heirarchy reference does not work

In reply to dave_59:

Apologies for not describing the working/not working term


 assign a1.C=b1.X; //working
 assign #1ps a1.D=b1.X; //not working

working : a1.C value is same as b1.X
not working : here the value a1.D is “X”.

Once the delay is applied, the value become “X”.