Never, fella. The disciples at the Last Supper were all Jews, still under the Mosaic/Davidic Covenant, and ordained to observe Seder, Jesus not yet having fully fulfilled The Law. The wine could only be at that point a symbol of The Blood of the New Covenant. There was no overlap of the two. And People of The Way, the Company of the Committed were not denominated "Christians" until long after, in the Antioch of Syria. So your question has no foundation and is irrelevant.
So it is your position that all the disciples who actually knew the Messiah are Jews and not Christians (who originated much later in Antioch of Syria as mentioned in the book of Acts). Further, you assert there was no overlap and yet the line of demarcation seems to be Antioch or perhaps the crucifixion. However, that feast of Shavuot occurred after not only the death of the Messiah, but his resurrection and Ascension as well.
The reality is the one holy catholic apostolic church bound new rules, feast days, and calendars for Christians to differentiate them from those still followed by Jews in all their generations. This includes the memorial of that special Passover in the daily Mass.