Update request with Dapper

I am using the following code to update my user table. The problem is that updated it returns 0 when the data used is the same with the data in database and 1 otherwise.

var query = @"UPDATE users SET
                firstname = @firstname,
                lastname = @lastname
                WHERE id = @userId";
var updated = await con.ExecuteAsync(query,
    new
    {
        firstname = user.firstname,
        lastname = user.lastname,
        userId = user.id
    });
return updated > 0;

For example:

1st try: firstname = "John", lastname = "Doe", userId = 1

Result = 1

2nd try: firstname = "John", lastname = "Doe", userId = 1

Result = 0

3rd try: firstname = "Johny", lastname = "Doe", userId = 1

Result = 1

Is this the expected behaviour?