Charcoal kiln on Wilson Trail, stage 5 [????- ]

Here's how it looks from the path (facing towards Sha Tin).

I've walked past here several times before without noticing this, so I wonder if there has been a recent collapse that makes it more obvious? At first I assumed it was a Japanese wartime tunnel, as there are several in this area. But when I looked closer the soil around the edge of the opening has that different look, caused by being baked by the heat of the charcoal fire.

Then looking inside there's the same narrow opening in the back wall for ventilation that we've seen in other charcoal kilns.