...another bit is that like the Saturn 128K card, and a few others,
these work in Slot 0 without any kind of connection to the
motherboard.

The Saturn 128K and some other Slot 1-7 cards could be used as
language cards and have the rest of the RAM available for other
purposes while giving up 16K for the 'language card' function.
--- SBBSecho 2.12-Win32