Why does string.join return list object in VB.Net

I am having trouble understanding the difference between these two commands that in my mind should do the same thing. I have posted the entire code below in case anything is unclear.

I have created two functions in class Person, one that returns a list containing first,middle and last names and one that returns a concatenated string of the name. I reference the function that returns the list to concatenate the string with the line below:

FullName = String.Join(" ", Me.Get_NameList())

However, when I call:

Console.WriteLine(Person1.Print_Name())

I get what looks like the list object instead of the string:

System.Collections.Generic.List`1[System.String]

If I change the code to look like this:

    Public Function Print_Name()
        Dim FullNameList As List(Of String) = Me.Get_NameList()
        Dim FullName As String
        FullName = String.Join(" ", FullNameList)
        Return FullName
    End Function

The console prints:

John Q Doe

Why am I getting a different answer by first assigning the list to a variable and then joining it? Does this have something to do with how the list is stored in memory?

Thanks in advance for the help.

Here is the full code:

Imports System
Module Module1
    Sub Main()
        Dim Person1 As New Person("John", "Q", "Doe")
        Console.WriteLine("Get_Name Values")
        Dim g1 As List(Of String) = Person1.Get_NameList()
        Console.WriteLine(String.Join(" ", g1))
        Console.WriteLine("Print_Name Values")
        Console.WriteLine(Person1.Print_Name())
    End Sub
End Module

Class Person
    Private FirstName As String
    Private MiddleName As String
    Private LastName As String
    Public Sub New(ByVal Fn As String, ByVal Mn As String, ByVal Ln As String)
        FirstName = Fn
        MiddleName = Mn
        LastName = Ln
    End Sub
    Public Function Get_NameList()
        Dim NameList As New List(Of String)
        NameList.Add(FirstName)
        NameList.Add(MiddleName)
        NameList.Add(LastName)
        Return NameList
    End Function
    Public Function Print_Name()
        'Dim FullNameList As List(Of String) = Me.Get_NameList()
        Dim FullName As String
        FullName = String.Join(" ", Me.Get_NameList())
        Return FullName
    End Function
End Class