I've read, in the Wybauw book, that the temperature differential between
chocolate and item to be dipped should not be more than 18F. This means that
if the working temp of the chocolate is 86F at the lowest, that the coolest
the room should be is 68F. This is not what I would consider a "cool"
room--at least not in the winter.

Well based on practical experience...If I dipped centers more t han 8
degree C cooler( equivalent to 18F) the chocolate tends to harden
undevenly....sometimes moisture condensation can even occur and that
can affect the quality of the coaitng.and the resulting product
In many cses if the centers are too cold the chocolate coating tends to
loosen up and flake off.

Therefore if the centers are kept under refrigeration I allow it to
thaw in the chocolate room ambient before I enrobed it to minimize the
temperature differential.
Besides the coating can bind better if the center is a bit warm.

If I back up filled shells with chocolate I even warm gently and
quickly the centers with a heat gun before I place the final coating.
to ensure a good adhesion