✅ Compiler limitation or is this logic wrong?

int state = 0;
switch (input.AsSpan(input.Length - 2, 2)) {
    case "KB": format = MemoryFormatType.KiloByte1024; break;
    case "MB": format = MemoryFormatType.MegaByte1024; break;
    case "GB": format = MemoryFormatType.GigaByte1024; break;
    case "TB": format = MemoryFormatType.TeraByte1024; break;
    default: state = 1; break;
}
if (state == 0) {
    return true;
}