He wanted to go all out and maximise "company form". Same as optimizing your website for hundred of thousands of visitors even if you have only like one hundred visitors...

If the parent comment is correct and this form is necessary for personal financial protection, I wouldn’t consider that “all out”.

That’s the bare minimum consideration for a viable company structure.

OP wanted to set up a nested copmany structure. Instead of Person -> LLC it goes Person -> Limited Partnership --> LLC. The in between company is only for tax-efficiency and has nothing to do with limited liability.

Even then you'd usually go with a Person -> Holding UG -> Startup UG structure. That's a few hours and less than a thousand Euros.

It’s not necessary. They did something completely overkill

It's not.

You get one chance at getting your company form right. Any other new chance costs a ton of money in restructuring. Software is malleable, companies are less so.

I am not familiar with German business entity structures, so this is very interesting.

So, if I started a sole proprietorship, it is not possible to convert it to a full blown, privately held corporation in Germany?

It is obviously possible, the process is probably very similar in effort and expenses to founding it in that form directly.