Is the field describe result map a special type of Map?

Question

I read in Accessing All Field Describe Results for an sObject:

Use the field describe result's getMap method to return a map that represents the relationship between all the field names (keys) and the field tokens (values) for an sObject.

Map<String, Schema.SObjectField> fieldMap = Schema.SObjectType.Account.fields.getMap();

The map has the following characteristics:

All field names are case insensitive.

While the documentation for Maps says:

Map keys of type String are case-sensitive.

QUESTION

Is the field describe result map a special type of Map? It's quite frustrating to have one type of Map in apex to behave differently.

Answer 1

In the object oriented "is a" sense, at least at compile time, they both support these Map methods. But the implementing class might be this for the describe map:

Map<String, String> m = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER);

and this for most other maps:

Map<String, String> m = new HashMap<String, String>();

Other languages would make the distinction between interface and implementation a bit clearer by providing the contract (the methods) in an interface.

I agree being case insensitive in some places but not in others can be confusing.