R”Moshe zz’l brings proof that no mechitza is needed by a “chasunoh” from korbon pessach- when families ate together and no separation was required to eat together. So, it seems pretty clear that we are talking about eating together-without separate seating.
There’s absolutely no indication that there was mixed seating (other than no mechitzah). It is clear, though, that there were separate families, yet no mechitzah.