Most of the production line is already roboticised. Less with Mercedes than say VW because Mercedes sells more leather seats and walnut interiors but by and large it's mostly robots.

Apptronik says that Mercedes is exploring use cases like having Apollo inspect and deliver components to human production line workers.

...I fail to see how that isn't better solved with logistics robots on rails or wheels. I suspect it's Apptronik coming to Mercedes and saying "hey wanna try this we pay" and Mercedes says "why not" and Apptronik goes "wee, cheap publicity".

wouldnt it make more sense to do a trial that tests their supposed advantages over purpose built robots rather than one which decidedly does not

Yeah but the article says the only thing these ones are gonna do is deliver parts which is probably overkill for the likely expense for the kind of sophistication necessary to imitate even a fraction of a human worker’s versatility. To say nothing about the difficulty involved in adapting them to various tasks without reprogramming or training.