Unexpected timezone display name

Two timezones, "Africa/Abidjan" and "Africa/Bamako", use the same display name,but interestingly TimeZone.toZoneId().getDisplayName() returns unexpected names.

=======================================================
In display name datafile (TimeZoneNames.java),
        String GMT[] = new String[] {"Greenwich Mean Time", "GMT",
                                     "Greenwich Mean Time", "GMT",
                                     "Greenwich Mean Time", "GMT"};

            {"Africa/Abidjan", GMT},
...
            {"Africa/Bamako", GMT},
=======================================================

Test program:
import static java.util.Locale.ENGLISH;
import static java.time.format.TextStyle.FULL;
import static java.time.format.TextStyle.SHORT;

    public static void main(String[] args) {
        TimeZone tz = TimeZone.getTimeZone("Africa/Abidjan");
        ZoneId id = tz.toZoneId();
        String name = id.getDisplayName(FULL, ENGLISH);
        System.out.println(name);
        name = id.getDisplayName(SHORT, ENGLISH);
        System.out.println(name);

        tz = TimeZone.getTimeZone("Africa/Bamako");
        id = tz.toZoneId();
        name = id.getDisplayName(FULL, ENGLISH);
        System.out.println(name);
        name = id.getDisplayName(SHORT, ENGLISH);
        System.out.println(name);

Result:
Africa/Abidjan <--- Strange
Africa/Abidjan <--- Strange
Greenwich Mean Time
GMT