Unclear description regarding equality of "K" and "zzz" time zone format specifier

[MichaelRomer]

Describe the issue or suggestion

The documentation states:

For DateTimeOffset values, the "K" format specifier is equivalent to the "zzz" format specifier [...]

while this may be the case for serialisation, this behaviour differs when deserializing time strings as shown in the example below.

const string inputWithOffset = "2023-08-31T07:00:00+02:00";
const string utcInput = "2023-08-31T07:00:00Z";
const string inputWithoutOffset = "2023-08-31T07:00:00";

DateTimeOffset.ParseExact(inputWithOffset, "yyyy'-'MM'-'dd'T'HH':'mm':'ssK", null, DateTimeStyles.None); //works
DateTimeOffset.ParseExact(utcInput, "yyyy'-'MM'-'dd'T'HH':'mm':'ssK", null, DateTimeStyles.None); //works
DateTimeOffset.ParseExact(inputWithoutOffset, "yyyy'-'MM'-'dd'T'HH':'mm':'ssK", null, DateTimeStyles.None); //works

DateTimeOffset.ParseExact(inputWithOffset, "yyyy'-'MM'-'dd'T'HH':'mm':'sszzz", null, DateTimeStyles.None); //works
DateTimeOffset.ParseExact(utcInput, "yyyy'-'MM'-'dd'T'HH':'mm':'sszzz", null, DateTimeStyles.None); //FormatException
DateTimeOffset.ParseExact(inputWithoutOffset, "yyyy'-'MM'-'dd'T'HH':'mm':'sszzz", null, DateTimeStyles.None); //FormatException

→ the "zzz" specifier does not allow the "Z" offset and a missing offset, while the "K" specifier accepts those.

I think this is worth to be mentioned in the documentation.