List.GetItemById Will Return Item with All Fields

It is a little surprise to me when I saw the List.GetItemById will return a item with all fields populated with data.

using (ClientContext context = new ClientContext(tbUrl.Text))
{

try
{

if (isOffice365)
{
...
}

Web web = context.Site.OpenWebById(currListInfo.WebId);
List list = web.Lists.GetById(currListInfo.ListId);

// GetItemById return item with all fields
ListItem item = list.GetItemById(60);
context.Load(item);
context.ExecuteQuery();

foreach (string fieldName in item.FieldValues.Keys)
{
LogInfo("Field Name = " + fieldName + " Value = " + item.FieldValues[fieldName]);
}
}
catch (Exception expt)
{
LogInfo(expt.Message + expt.StackTrace);
}

On the other hand using GetItems as next code, you have to specify the fields to be returned in the LINQ.

try
{

Web web = context.Site.OpenWebById(currListInfo.WebId);
List list = web.Lists.GetById(currListInfo.ListId);
string queryTxt = "<View><Query><Where><Contains><FieldRef Name=\"Title\" /><Value Type=\"Text\">Auto</Value></Contains></Where></Query></View>";
CamlQuery query = new CamlQuery();
query.ViewXml = queryTxt;
ListItemCollection listItems = list.GetItems(query);

context.Load(listItems, items => items.Include(item => item.Id,item => item["Title"], item => item["helloworld"], item => item["myField"]));
context.ExecuteQuery();

foreach (ListItem item in listItems)
{
LogInfo("Item ID = " + item.Id + " Title = " + item["Title"] + " helloworld= " + item["helloworld"] + " myField= " + item["myField"]);}
}
catch (Exception expt)

{

LogInfo(expt.Message + expt.StackTrace);