Clarify clear facts (#50667)

* Revert "avoid x2 setting of set_fact when 'cacheable' (#50564)"

This reverts commit 207848f354.

* clarify clear_facts with set_fact cacheable

 revert previous 'fix' as it will break playbooks by changing precedence
 opted to leave current behaviour but document it on both plugins to mitigate confusion

 fixes #50556

 also fix grammer, add comment, remove unused e

lib/ansible/modules/utilities/logic/set_fact.py

@@ -40,6 +40,9 @@ options:
       - Normally this module creates 'host level variables' and has much higher precedence, this option changes the nature and precedence
         (by 7 steps) of the variable created.
         https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable
+      - "This actually creates 2 copies of the variable, a normal 'set_fact' host variable with high precedence and
+        a lower 'ansible_fact' one that is available for persistance via the facts cache plugin.
+        This creates a possibly confusing interaction with ``meta: clear_facts`` as it will remove the 'ansible_fact' but not the host variable."
     type: bool
     default: 'no'
     version_added: "2.4"