Help with PowerShell $PSBoundParameters

My script below works and that should satisfy it's purpose, however, I am trying to learn more about what is happening.

In doing so I have put Write-Verbose within an If/Then process so that if the computer name is passed as a parameter it should Write-Verbose that it is passed as a parameter. However, if passed as a script, it should Write-Verbose that it is passed through pipeline.

Why in every example does the computer name(s) pass through as parameter??

Get-Content .\list.txt | Start-ReportPSCompliant -Verbose

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That should pass the computer names through the cmdlet as pipeline and the Write-Verbose "$_ is going through pipeline" should be printed, but no matter how I use the cmdlet it always passes through as parameter.

Why is it not using the pipeline Else{} script??

function Start-ReportPSCompliant {
<#
.Synopsis
   This reports on computers as to whether or not they have policy ready for PSRemoting by invoking a command to return the environment computer name. If it doesn't return then PSRemoting is not enabled or the device is unavailable.
.DESCRIPTION
   Enter in a single computer name or multiple computer names. Value from pipeline is also
   acceptable.
.EXAMPLE
   Start-ReportPSCompliant Server1

.EXAMPLE
   Start-ReportPSCompliant -Computer 'computer1','computer2'

.EXAMPLE
   Get-Content C:\Scripts\list.txt | Start-ReportPSCompliant 

.EXAMPLE
   Start-ReportPSCompliant (Get-Content C:\Scripts\list.txt)
#>

    [CmdletBinding()]
    Param (
        [Parameter(Mandatory=$true,ValueFromPipeline=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=0)]
        [String[]]$Computer = 'localhost'
    )
    Begin {
        Write-Verbose 'Looking for existing reports and removing files if found'
        $Pa = Test-Path C:\Scripts\temp\compliant.txt

            if ($Pa) {Remove-Item C:\Scripts\temp\compliant.txt; Write-Verbose 'compliant.txt list was removed'}
            else {Write-Verbose 'compliant.txt list does not exist'}

        $Pa = Test-Path C:\Scripts\temp\noncompliant.txt

            if ($Pa) {Remove-Item C:\Scripts\temp\noncompliant.txt; Write-Verbose 'noncompliant.txt list was removed'}
            else {Write-Verbose 'noncompliant.txt list does not exist'}

    }
    Process {
        if ($PSBoundParameters.ContainsKey('computer')) {
             # we have parameter input
        Write-Verbose "$Computer is going through as parameter input"
             foreach ($c in $Computer) {
                CompliantWorker $c
             }
        }else{
             # we have pipeline input
        Write-Verbose "$_ is going through pipeline"
             CompliantWorker $_
        }
    }
    End {
        Write-Verbose 'The operation is complete'
        $Pa = Test-Path C:\Scripts\temp\compliant.txt

            if ($Pa) {notepad C:\Scripts\temp\compliant.txt}
            else {Write-Warning 'No computers in list were compliant!'}

        $Pa = Test-Path C:\Scripts\temp\noncompliant.txt
        
            if ($Pa) {notepad C:\Scripts\temp\noncompliant.txt}
            else {Write-Verbose 'All computers in list were compliant!'}
    }
}
function CompliantWorker {
    param (
        $Computer
    )
        Write-Verbose "Attempting to send a remote command to $Computer"
        Invoke-Command $Computer {$env:COMPUTERNAME} -ErrorAction SilentlyContinue -ErrorVariable err
        
            if($err.count -gt 0) {
                Write-Output $Computer | Out-File C:\Scripts\temp\noncompliant.txt -Append
            }
            else {
               $Computer | Out-File C:\Scripts\temp\compliant.txt -Append
            }
}

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