Mitko is exactly right. What’s you’re seeing is a slave board - just a spring with two wires on the back going to a nanjg105c that’s floating around inside the pill. If you’re going to go through the effort of opening it up (worth it!), throw a proper FET+1 driver in there. I’ve modified 10+ of them in this way. If you didn’t get the XP-L HI version, that LED works great in the B158. If you’re going FET+1, make sure to get it on a DTP board (Noctigon, Sinkpad). Set the 105c aside to use in something else.
The slave board is soldered to a ring that is press-fit into the pill. To me, the easiest way I’ve found to remove it is to unsolder the LED and push the wires down into the pill. Put the pill in a vise or something (with proper padding) and poke a small nail through an opening for the wires. Pointing the nail to the outside (so as not to damage the 105c), tap lightly with a hammer. It should come out with light pressure.
The second post in this thread has some good photos and info. No need to mangle the setup like in the photo, though. The process I’ve been doing works nicely, and then you can re-use that brass ring. To me, it’s easier than soldering to the pill.