newb question: why is a foreach Item different from a Get-Item Item?!?

Here's my simple function test script and two use case tests:

# test rig for new function

function Test-FileNewerThanRefDate{
    # return True if $vFile is new than $vRefDate, else return False

    param(
        $vFile,
        [datetime] $vRefDate
    )
    if (($vFile.get_LastWriteTime() -gt $vRefDate) -or ($vFile.get_CreationTime() -gt $vRefDate)) {
        return $true
    } else {
        return $false
    }

}

$TestRefDate=[datetime]"9/30/2019"

# CASE #1
$Test1="\\DS218plus\home\other PSE catalogs\CMS 1976-7\CMS holiday 1976 00.jpg"
$Test2="\\DS218plus\home\other PSE catalogs\CMS 1976-7\IMG-3679.JPG"
$Test3="\\DS218plus\home\other PSE catalogs\CMS 1976-7\Thumbs.db"

foreach ($vTestCase in ($Test1, $Test2, $Test3)) {
    if (Test-FileNewerThanRefDate (Get-Item $vTestCase -Force) $TestRefDate) {
        Write-Host("newer")
    }
}

# CASE #2
$TestPath="\\DS218plus\home\other PSE catalogs\CMS 1976-7\"

$vItems = Get-ChildItem -LiteralPath $TestPath -Force

foreach ($vItem in $vItems) {

    if (-not ($vItem.PSIsContainer)) {
        if (Test-FileNewerThanRefDate($vItem, $TestRefDate)) {
            Write-Host("$vItem is newer")
        }
    }

}

The first use case works as desired; the function is correctly able to evaluate the creation and last write timestamps for the Get-Item() returned file.

The second use case fails. For some reason, the foreach ($vItem in $vItems) of the Get-ChildItems() list of items is getting passed to the function as a [System.DateTime] not a file-like object. The resulting error is:

Method invocation failed because [System.DateTime] does not contain a method named 'get_LastWriteTime'.
At C:\Users\lgg\Desktop\test.ps1:10 char:9
+ if (($vFile.get_LastWriteTime() -gt $vRefDate) -or ($vFile.get_Cr ...
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Why is the foreach item a different type of object than the Get-Item() object? What is the correct way to do this?

Thanks in advance for any suggestions or advice!