In this code in java.time.Instant:

    public int get(TemporalField field) {
        if (field instanceof ChronoField) {
            switch ((ChronoField) field) {
                case NANO_OF_SECOND: return nanos;
                case MICRO_OF_SECOND: return nanos / 1000;
                case MILLI_OF_SECOND: return nanos / 1000_000;
                case INSTANT_SECONDS: INSTANT_SECONDS.checkValidIntValue(seconds);
            }
            throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
        }
        return range(field).checkValidIntValue(field.getFrom(this), field);
    }

the INSTANT_SECONDS block falls through. The result is that passing INSTANT_SECONDS to the method sometimes throws DateTimeException and sometimes throws UnsupportedTemporalTypeException.

The correct behaviour (as per the spec) is to throw UnsupportedTemporalTypeException. As such the whole "case INSTANT_SECONDS" line should simply be removed.

See also https://github.com/ThreeTen/threetenbp/issues/41 for context.