When specifying custom fields the docs state that for the unique key 'This is not often used but it can be used by 3rd party extensions or developers to retrieve a value of the custom field.'

Does this mean that if you had for example two profiles A and B both with a field "Home telephone" and a developer wanted to access this custom field in profile A that the key should be unique for each field (e.g. 'a_home_tel', 'b_home_tel')? Surely the field would be identified by both the profile ID and the field?

I ask because I just want to make sure I set up the fields correctly.