We were just there as a group of 20 is December and they told us the same thing when we booked, but ended up sitting relatively close to each other at all the restaurants. We never sat at one big table, but were always at tables next to each other.
I tried to book Le Cellier but was told that they couldn’t take parties that large and that we could book 3 separete ressies, but then we would have to be there at least an hour early just to tell the CMs working that we were together and would like to sit near each other. Too much of a headache IMO, so I booked somewhere else. Good luck!