I think it is a gain stage module for the preamp.
It is probably best to contact Jeff Rowland again to answer your question. While I've never spoke to him on the phone, he is quite good at replying to e-mails. Generally speaking, a module is an enclosed electrical system. What would be in that closed electrical system is up to the designer and the design.
Audiogal2, a module is usually a smallish electronic board, populated by chips or discrete devices, and sometimes sealed in a housing or epoxy matrix. Modules may be soldered onto the machine or plugged into sockets. If you have questions specific to your Consonance, buzz Jeff. He is still quite approachable and Rowland keeps a complete computer log of all maintenance work performed on most all JRDG machines that come in for TLC.
As Dazzdax said it's the gain stage for the preamp.
The Consummate and Consonnance both had plug-in modules for the gain stage. Over time these modules do fail and need to be replaced. Depending on the vintage you're dealing with the modules may or may not be potted in epoxy resin.
If you look at the photo of the Consummate on the Rowland website you can see the modules.
The pre-amp section is furthest back in the photo and the "modules" are the large black rectangular boxes mounted to the board.
By "up to date" he likely meant that you now have the most current revision of the module that was replaced and that the unit is within spec. It doesn't mean that he integrated any new technology. In other words, he didn't change your unit into a Concerto or Synergy...