Diagonal directions can extend the "game's engine distance" much more. The game "reads it" as a longer distance, than it can be seen with a naked eye.

Therefore, when you use a traditional girder power, like in Intermediate/Team17, you can place the girder maximum 4 long girders away from you when you put it on the same height on your right or left. But as soon as you wish to place it diagonally upwards or downwards (especially at 45 degrees), the maximum distance would be 3 long girders.

The distance is of course counted as the one from your worm and the exact center of the girder that you wish to place.

EDIT: I found one very bizarre replay from one game with danie, where a worm squeezed into a tunnel with mine inside, but the mine somehow didn't explode as well. None of us could figure out how this happened. (attachment)

TIME 1:50 & 4:17