Not necessarily. When a speckle data stream is uploaded it is stored in server, with an identifier and a meaningful comment. The actual federation would happen when a user actively downloads data streams of his choice to a particular application.
note that a "federation" in that context could mean getting one data stream uploaded from Rhino representing geometry (speckle mesh), another data stream uploaded from excel with a bunch of data (speckle dictionary), and finally downloading them in a third application joining/federating everything together (supposing that the particular implementation of "speckle for Archicad" was designed to make sense of that particular combination of geometry+dictionary, lets say that in Archicad this is converted to a slab with properties. Each connector implementation is capable of making sense of a particular set of data types. Speckle is mainly a development platform and its full potential flourish when one is capable of adapting the tool (writing code) to its needs.
Or it could be simply that I upload two data streams from rhino representing (two) meshes (wich are stored in the speckle server not repeating the data structure of a rhino mesh, but other one, for that particular case speckle already has its own data structure to represent a "mesh") and then each one these streams is downloaded from Archicad as a morph (supposing that the connector converts "speckle meshes" to morphs.