@Bobcat, yes... I was starting to look for the reference that changed that understanding, but got swept away with absolutely astounding references that said outright that the other sheep are not members of the body of Christ and are not sons of God. This is a topic that they've been resolute on for a very long time and is said quite often in the Watchtower, those in more recent decades it phrases it something along the lines "The limited number of Christians chosen by Jehovah to be associated with Christ in the heavenly Kingdom government undergo “a new birth” as spirit-begotten sons of God." (w12 3/15 p. 21 par 4.) This subtle phrasing makes it easy to miss that not every JW is a son of God or a member of the body of the Christ.
So, their line of reasoning has been all along:
Christ only had the 11 present (they maintain Judas left), thus showing that only those qualified to rule as kings with Christ would be permitted to partake of the emblems. And only those who partake are considered sons of God and members of the body of Christ.
w51 1/15 p. 444-49 has an article that explains the whole Judas thing where they feel that yes, he partook of the Passover meal, but not the Lord's meal. Their reasoning comes down to the fact that Jesus gave Judas the dipped morsel, whereas the loaf that was broken was not dipped.
Personally, I don't think that matters at all. Whether Judas was present or not is immaterial to all those who proclaim to follow Christ, even if they are not of the 144,000. Jesus gave the directive in John 6:53 for everyone to partake, and he said that unless you do, you cannot have life in yourself. He never, ever limited eating to the 144,000. He didn't limit it to the "little flock" either. No such prohibition is place on it anywhere in the scriptures. To say that the "great crowd" cannot partake is putting them in the same class of people as Judas Iscariot.
Sorry, this was off topic. I had to rant a little. Back to our regularly scheduled program...