implicit_case_default: updated explanation

md/syntaxrules-explanation-implicit_case_default.md

@@ -3,22 +3,34 @@ default to be implicitly defined. Case statements without a `default` branch
 can cause signals to be undriven. Setting default values of signals at the top
 of an `always` procedures is good practice and ensures that signals are never
 metastable when a case match fails. For example,
+
 ```sv
 always_comb begin
   y = 0;
-  case(x)
+  case (x)
     1: y = 1;
   endcase
 end
 
 ```
-If the case match fails, `y` wouldn't infer memory or be undriven because the
-default value is defined before the `case`.
+
+If the case match on `x` fails, `y` would not infer memory or be undriven
+because the default value is defined before the `case`.
+
+This rule is a more lenient version of `case_default`. It adapts to a specific
+coding style of setting default values to signals at the top of a procedural
+block to ensure that signals have a default value regardless of the logic in the
+procedural block. As such, this rule will only consider values set
+**unconditionally** at the top of the procedural block as a default and will
+disregard assignments made in conditional blocks like `if`/`else`, etc. If this
+coding style is not preferred, it is strongly suggested to use the rules
+mentioned below as they offer stricter guarantees.
 
 See also:
- - **case_default**
- - **explicit_case_default**
+
+- **case_default**
+- **explicit_case_default**
 
 The most relevant clauses of IEEE1800-2017 are:
-- 12.5 Case statement
 
+- 12.5 Case statement