Workbooks.Open causes memory leak

Question

In production vba, when opening excel file in a specific folder in loop I saw excel devours memory and finally causes a memory leak. I wrote short codes to investigate its root cause and facing the following questions.

Question.1

In loop it just opens and closes workbook but excel's memory usage increases. It seems some object is not released but I don't understand (a) which one is and (b) what's the problem of this code.

Sub Test01()
    Dim fso As FileSystemObject
    Set fso = New FileSystemObject
    Dim f As File
    Dim wb As Workbook

    Application.EnableEvents = False
    Application.Calculation = xlCalculationManual
    Application.ScreenUpdating = False

    Dim Files As Variant
    Set Files = fso.GetFolder("*****").Files
    For Each f In Files
        Set wb = Workbooks.Open(f.Path)
        wb.Close savechanges:=False
        Set wb = Nothing
    Next

    Application.EnableEvents = True
    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True
End Sub

Question.2

I found that a use of COM object can be a solution. Indeed it starts another process and its memory usage never shows weird increase but I don't understand its reason because codes in loop are almost identical. Why this code doesn't lead a memory leak?

Sub Test02()
    Dim fso As FileSystemObject
    Set fso = New FileSystemObject
    Dim f As File
    Dim wb As Workbook

    Dim oxl As Excel.Application
    Set oxl = CreateObject("Excel.Application")
    oxl.Visible = False

    Application.EnableEvents = False
    Application.Calculation = xlCalculationManual
    Application.ScreenUpdating = False

    Dim Files As Variant
    Set Files = fso.GetFolder("*****").Files
    For Each f In Files
        Set wb = oxl.Workbooks.Open(f.Path)
        wb.Close savechanges:=False
        Set wb = Nothing
    Next
    oxl.Application.Quit
    Set oxl = Nothing

    Application.EnableEvents = True
    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True
End Sub

Please note that;

1. folder contains 3000 excel files so that loop is done 3000 times

2. file size of excel files is less than 15kb

Detailed response to @braX

I think you answered to Question.2 and intended a code like this. I understand that storing oxl.Workbooks improves performance than calling oxl.Workbooks every time, but in a perspective of memory usage it seems like a different story because Workbooks should be released out of the loop.

    Dim wbs as Workbooks
    Set wbs = oxl.Workbooks
    Dim Files As Variant
    Set Files = fso.GetFolder("*****").Files
    For Each f In Files
        Set wb = wbs.Open(f.Path)
        wb.Close savechanges:=False
        Set wb = Nothing
    Next
    Set wbs = Nothing
    oxl.Application.Quit
    Set oxl = Nothing