Surprisingly, the naturally-packed piles don’t burn that well. Oh, they’ll burn, but not that hotly. There’s too much air gap between the burning fuel. You have to crush them down to a more dense fuel... then they’ll burn like a fury.
Where we farmed in Nevada, sometimes we’d get a half-section of tumbleweeds blowing in on us and trapped up against the fences for a mile of fence.
I’d push them off the fence with the backhoe, then push them up into a pile and then crush them down with the front bucket. When I was done with a mile of fence, I might have... oh, six to eight piles of tumbleweeds (russian thistle and kochia) 10’ high and packed really tightly.
We’d then wait until about 0300, call the fire dispatcher and tell them we were doing a controlled burn. We’d wait until about 0300 because that’s when the wind would be dead calm.
When those packed 10’ piles would go up, the heat coming off those piles would blister your skin 125’ away. I’d usually set up the pile with a ring of gasoline at the base to get the whole thing going up as quickly as possible so that I could get all the piles burned in an hour or so, then clean up the embers before dawn.
I agree with you but still…. If my house was buried in the stuff like some of those pictures and some guy was walking around flicking lit cigarette butts into the pile, I think that I’d be a bit concerned.