Clarify "YAML Shortcomings" documentation

[anno1985]

The section on YAML Shortcomings in the docs on Externalized Configuration states:

Using the multi YAML document syntax in profile-specific YAML files can lead to unexpected behavior.

It goes on to give an example for "a file called application-dev.yml, with the dev profile being active":

server:
  port: 8000
---
spring:
  profiles: !test
  security:
    user:
      password: weak

It concludes by stating:

In the example above, profile negation and profile expressions will not behave as expected.

However, it fails to mention what the actual result of the combination is, and why it would be unexpected. (It isn't explicitly stating what the author would have expected, so it's not clear what the actual/unexpected outcome would look like.)

It would be nice if the docs could be expanded to include what the issue/unexpected behaviour actually is.