I only have one Dandelion chip, on a BR2, and got curious so I had to check it out as I had yet to use it on the Z8. What I find is that to make it register the focal length programmed into it when mounted on the Z8 via the FTC II adapter, it has to be mounted while the camera is turned on. Then IBIS then works and is available in the menu, otherwise it does not register at all and Z8 will use any non-cpu data that is already set at the time to guide the IBIS. So the trick to make my Dandelion work on the Z8 after mounting normally with camera off (to protect sensor against dust) is to then twist it to half dismounted and back again with camera turned on. I cannot verify the effectiveness, but I can then hear IS working when I expose and it is turned on in the menu. My Dandelion is quite old, from 2011 or earlier, and from the above it would seem like the design might have changed, or perhaps different camera models respond differently. (My Dandelion version is the one that registers as a G-chip.)
This seems to be part of the same problem as with Birna's chips that do not fully register after being mounted while Z8 is off, but opposed to with the Dandelion, Z8 will register correct EXIF data in other fields than the Lens Model field so that IBIS works without using the above trick.