Hmmm not totally. A bad actor could record the keyboard and then figure out a way to get it installed. Either through a logistics attack (not everyone maintains a secure supply chain), or an insider threat installing it. Everyone's trained not to allow thumb drives and the like. But a 100% completely unaltered bog standard keyboard brought into a building is probably easier, and for sure less suspicious if you get caught.
Sure you might say, "but if you have an insider you've already lost" to which I say, your insider is at risk if they do certain things. But once this keyboard is installed, their own detection risk is less.
Now the question is, how far away can the mic be? Because that's gonna be suspicious AF getting that installed. BUT!!! this is still a great way to break the air gap.