I'm asking because i thought of a circuit network where i could send a spidertron from dock to dock (with the recal function) and use it like a bigger logistic robot. Doesn't docking the Spidertron passively make it impossible?
It's still possible, don't worry. The circuit connection behaviour is exactly the same, regardless of the docking mode.
But why has the Spidertron have to be passively docked?
It's more for technical reasons. If I would allow it as well for actively docked spiders then there would be two ways of inserting into the inventory, through the spider itself (like logistic requests) and through the interface chest. This is not really easily possible, and I will have to duplicate the items between the two inventories, and then keep them in synchronization with each other, and that will become a mess of complex code and likely duplication bugs.
I feel it's a fair trade-off that you can only access its inventory when the spider is docked in passive mode. It's like it need to shut it's systems down to connect that thoroughly with the dock, and that prevents its equipment from functioning or whatever :)