docs: clarify the shortcomings of local variable technique for parent…

…-child component interactions (#42331)

Closes #38302

PR Close #42331

aio/content/guide/component-interaction.md

@@ -300,8 +300,11 @@ The *local variable* approach is easy. But it is limited because
 the parent-child wiring must be done entirely within the parent template.
 The parent component *itself* has no access to the child.
 
-You can't use the *local variable* technique if an instance of the parent component *class*
-must read or write child component values or must call child component methods.
+You can't use the *local variable* technique if the parent component's *class* relies on the
+child component's *class*.  The parent-child relationship of the components is not established
+within each components respective *class* with the *local variable* technique.  Since the *class*
+instances are not connected to one another, the parent *class* cannot access the child *class*
+properties and methods.
 
 When the parent component *class* requires that kind of access,
 ***inject*** the child component into the parent as a *ViewChild*.