This seems like a pretty reasonable objection and not just "complaints are just for complaint's sake".
The Tesla factory is a huge exception, mostly because Tesla went ahead using temporary permits and took the risk that the final permits may be denied. The project has a lot of political support, which also helped the process along.
On one end of the spectrum we have environmental groups making objections against every tiny detail.
On the other end we have - “Highly poisonous gas escaping the factory into the environment? What evidence is there that it is a serious problem?”. A very Nestle approach
I have no idea if thats true, how big the risks are or if things already have been cleared in the normal procedures.
This isn't the first factory in Germany and one would hope they know how to build them safely but who really knows.