$PSBoundParameters + $PSDefaultParameterValues[Cmdlet] = bug by S.K. _

# CASE1: function
PS > function aaa ( [Parameter(ValueFromPipeline)]$aaa, $bbb, $ccc , $ddd ) { }
PS > $PSDefaultParameterValues['aaa:ddd'] = { $PSBoundParameters >> aaa.log }
PS > 1..5 | aaa -bbb BBB -ccc CCC
PS > cat .\aaa.log

Key                                 Value
---                                 -----
bbb                                 BBB
ccc                                 CCC
aaa                                 1

... 2,3,4 ...

Key                                 Value
---                                 -----
bbb                                 BBB
ccc                                 CCC
aaa                                 5


Parameters are reflected in $PSBoundParameters.



# CASE2: Cmdlet
PS > $PSDefaultParameterValues['Get-ChildItem:Force'] = { $PSBoundParameters >> bbb.log }

PS > $PSDefaultParameterValues['Get-ChildItem:Force'] = {
     "`n---`$args[0].BoundParameters---" >> bbb.log
     $args[0].BoundParameters >> bbb.log
     "`n+++`$PSBoundParameters+++" >> bbb.log
     $PSBoundParameters >> bbb.log
     }

PS > ls -path .\aaa.log -File -Verbose
PS > cat bbb.log

---$args[0].BoundParameters---
Path
Verbose

+++$PSBoundParameters+++

---$args[0].BoundParameters---
Path
Verbose
File

+++$PSBoundParameters+++

---$args[0].BoundParameters---
Path
Verbose
File

+++$PSBoundParameters+++


Parameters are not reflected in $PSBoundParameters.