Dispenser over-activation behavior

So, this is the little problem I am in.
When I was informed about the new capacity of dispensers to shoot activated TNTs, I tried to build an automatic TNT canon with every TNT to be easily controlled by a serie of levers, and a few buttons.
But the fact is (as shown in the images I sent as attachments) that the redstone power did not only activated the good dispenser, but also adjacent ones. When the redstone circuit was at the same y level than the dispensers, it activated the good one, but also the one to his left, and the one to his right.
And when the redstone signal was one block higher in y than the dispenser, it also activated a dispenser two blocks higher in y than the "good" dispenser.
These two cases do not happen in the actual Minecraft (or if they do, sorry for the lost of time), so I report this strange dispenser behavior so that maybe, if it is a non-plannified problem, Mojang shall fix it. Else, again, sorry for the lost of time.

Notice that in the second case, the dispenser two blocks higher only activates if there is a bloc between the two dispensers.

My thanks to you for the reading,
Ruenruotel.

Post-Scriptum: I have joined an excedent of images, to be the most clear I can be.