Why does this not pass

[Imperatorn via Digitalmars-d-learn]

Why does all these pass:
    static assert(is(ElementEncodingType!(char[]) == char));
    static assert(is(ElementEncodingType!(wstring) == 
immutable(wchar)));
    static assert(is(ElementEncodingType!(byte[]) == byte));
    static assert(is(ElementEncodingType!(ubyte[]) == ubyte));
    auto range = iota(0, 10);
    static assert(is(ElementEncodingType!(typeof(range)) == int));
    static assert(is(ElementEncodingType!(immutable(ubyte)[]) == 
immutable(ubyte)));

But not this:
    static assert(is(ElementEncodingType!(AsciiChar[]) == 
AsciiChar));