Why does Move-Item nest an existing folder instead of merging its contents?

The issue is that the destination is being built as "$DestinationPath/$($_.Name)". When that path already exists as a directory, Move-Item interprets it as the directory that should contain the item, so the source folder is placed inside it.

If you want to move each item from the source directly into the destination, pass the destination directory itself:

Move-Item -Path $_ -Destination $DestinationPath -Force

Also make sure $DestinationPath is the parent directory where the items should land, not the path of the existing same-named folder. The -Force parameter allows overwriting or creating items where supported; it does not merge two directories.

For a folder move, provide only the destination parent path. For example, moving /source/synced_imgs to /destination should produce /destination/synced_imgs. Explicitly passing /destination/synced_imgs tells PowerShell that the existing folder is the destination container, so the source folder becomes a child of it.

If the goal is to merge directory contents recursively, Move-Item alone is not a full directory-merge operation. You need to enumerate the files, recreate their relative directories under the destination, and then move each file. A copy or synchronization tool can also be more suitable when preserving an entire tree.

The function call should look like this:

PSTransfer -BasePath /Users/user/BasePath -DestinationPath /Users/user/DestinationPath

Inside the loop, use:

Move-Item -Path $_ -Destination $DestinationPath -Force

Do not append $_.Name to the destination unless you are intentionally supplying a new target path. The extra name is what causes the existing folder to be treated as a container and produces the nested result.