Japanese Tunnel at Black Point [????- ]

I was doing a bit of unrelated research when I came across an interesting EIA report (https://www.epd.gov.hk/eia/register/report/eiareport/eia_1252006/html/ex...). It seems that back in 2006 there was a plan to build a Liquid Natural Gas (LNG) receiving terminal at Black Point (https://goo.gl/maps/eTRsMMFojdxTUNu2A), though it appears to have been subsequently abandoned.

In this report it was stated that as part of the cultural assessment a "WWII Cave" had been located at the site at a location named "Terrace 2" (attached image). I couldn't find any mention of it on Gwulo, so I did a bit of digging. It seems they did indeed find a (most likely) Japanese cave there, though disappointingly it appears that it was only about 2m deep (images attached).

Does anyone (more historically literate perhaps) know why there would be a cave at such a remote and inaccessible location? Additionally, if there is a Japanese cave here, could there perhaps be more interesting locations or artefacts in the area? I found very little reference to Black Point in any documentation I could find online. I am personally not able to visit this tunnel right now, so cannot verify that it is still there, though I can't imagine why it wouldn't be.