This clean up procedure shall be implemented into CCleaner
https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/clean-up-the-winsxs-folder
How would know if Avast/Piriform will add that into CCleaner?
From looking at the documentation why would CCleaner even need to bother with it at all, it is already taken care of by operating system itself.
WinSxS (Windows Side by Side) is sometimes refered to as the equivalent of the old i386 folder, a backup of your system files. - But it is much more complicated than that.
Whilst you could remove i386 if you were short of space, Windows needs some (most) of the components in Win SxS to run properly.
Removing WinSxS, or it's files, could break your Windows, resulting in BSOD's etc.
It clearly states in that link given above -
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Deleting files from the WinSxS folder or deleting the entire WinSxS folder may severely damage your system so that your PC might not boot and make it impossible to update.
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Leave it to Windows to clean and optimise WinSxS automatically, - or run Disk Clean-up, or Storage Sense 'Free up space now' if you must.
If you want to check just how big your WinSxS is, and if Windows recommends cleaning it, then see this link:
- Some files that supposedly stored in the "C:\windows\syswow64" and/or "c:\windows\system32" are/can be actual stored in one of those many sub-folders in the "c:\windows\winsxs" folder. In other words: DO NOT touch it !!! Or use the build-in Windows clean up tool.
I remember from many years ago there was some discussion about it, perhaps on this forum (not sure), but the gist of it was leave WinSxS alone.