Yes I agree. I'missing that too.Only solution I see is a Spy.
Later in same article
"Now, a few words about war. You can get control over a territory by “convincing” its owner or administrator to give a delegation to you, or, more traditionally, you can enter it, find the territory unit, destroy it and plant your own, or simply hack it. Expect it to be well hidden and well defended. "
It should not be easy to take ower a terrotiry.
If TU is rare and wery difficult to get. It may be much more difficult to desroy it.
I would be wery disappointed if one can just drill a hole into a wall or digg a tunnel..... to be able to destroy something so important.