question on "git subtree split"

Hello,

I'm splitting the directories of one large repository into multiple 
repositories using "git subtree split".
Everything is clear and understandable thanks to 
https://stackoverflow.com/questions/359424/detach-move-subdirectory-into-separate-git-repository#17864475
The new branch is created and contains exactly the expected commits.

But the oldest commit from the new branch is not connected to the 
initial (empty) commit of the repository.
Instead, it is a new parent-less commit.
This causes problems with some of the next operations that I need to 
perform as project cleanup, like squashing/re-ordering commits.

Is this intentional that the oldest commit of the new branch is parent-less?

Erwin