Power is generally the last thing people setup when adding to their factory, especially since the connections per pole is so low. Currently, until power is up and running the input is completely blocked off.
That, to me does not make sense. The input is just a big buffer bin the machine pulls from therefore it should be able to fill in regardless of the powered status of the machine itself.
If we look at it in real life terms (I know the game isn't real life but still) Just because the blast furnace in a steel mill is not currently running a campaign doesn't mean the stock room can't receive deliveries of iron, coke and limestone for the next campaign.