[doc][core] Wording corrections after PR review.

Author: claireguyot

docs/handbook/configuration.md

@@ -4,7 +4,7 @@
 
 Any task in a workflow can be declared as non-critical. A non-critical task is a task that doesn't trigger a global environment ERROR in case of failure. The state of a non-critical task doesn't affect the environment state in any way.
 
-To declare a task as non-critical, a line has to be added in the corresponding workflow template. Under the task role, in the `task` section (usually after the `load` statement), the line to add is `critical: false`, like in the following example:
+To declare a task as non-critical, a line has to be added in the task role block within a workflow template file. Specifically, in the task section of such a task role (usually after the `load` statement), the line to add is `critical: false`, like in the following example:
 
 ```yaml
 roles:
@@ -14,4 +14,6 @@ roles:
     task:
       load: mytask
       critical: false
-```
+```
+
+In the absence of an explicit `critical` trait for a given task role, the assumed default value is `critical: true`.