Not a bug. It is required to craft programmable speakers, none of the dependency technologies unlocks iron sticks, they need to be unlocked by some technology and we do not want to have "iron stick" technology introduced. Because of this, iron-stick recipe is unlocked in couple of places (railway ...

As the topic subject title says. I checked it (probably unreasonably) that it applies to English translation of the game as well. Also, players are allowed to use circuit cables before this research for some odd reason.