System User Messages template does not support EE Tags

[wardourdigital]

Description of the problem

Today I was trying to setup a custom template for the System User Messages template. I was glad to see in the docs it says that you can use any EE tags. So simply trying to use {layout="layout/_base"} so that the message would be wrapped in sites basic layout.

When the view is loaded the result is that the tags are not parsed and are output to the page.

EE Version: 7.2.6

How To Reproduce
Steps to reproduce the behavior:

1. Go to, System Message Templates and edit User Messages
2. In the template use a template variable or layout tag
3. Trigger the view load e.g Submit a form to see the thank you

Error Messages
No error messages, but you see the EE tags are not parsed but output to the page

[intoeetive]

@wardourdigital I wasn't able to replicate this when using system_messages/generic template and {layout} tag