I think in this context, the word emulate is being used to mean a modern hardware device being used to recreate the functions of an original "black box" chip. Where "black box" implies not everything may be known about how/why it works as it does.
A lot of reverse engineering has been done. Some of the assumptions made earlier on with ULA recreations were found not to be 100% correct. So "emulate" is used to describe it in case there are minor differences.
Anyway, that's my thoughts.