The Reasoning book under "Memorial" addresses John 6:54. It points out that the people (including the disciples) who heard Jesus say those words had no idea of a "Memorial" or Lord's Evening Meal. Thus, according to the WT, John 6:54 can't be applied to partaking of the emblems.
That logic is, of course, faulty. For example, the "audience" listening to Jesus included the readers of the fourth gospel who had been 'remembering' the Lord's Evening Meal for many years and would have easily seen the correspondence between John 6:54 and the symbolism involved in partaking of the emblems.
Another problem, if one accepts the WT's logic on why John 6:54 does not refer to partaking, then, that same logic would mean that Acts 15:29 can have no reference to blood transfusions since the original readers of the letter that contained Acts 15:29 had never heard of blood transfusions. I pointed this out to a brother some years ago and he acknowledged that 'the Society's reasoning has many holes in it.' Him and his wife have since pulled away from the WT (but not just for that).
A post I made on this page has a commentary reference concerning John 6:54 and the memorial emblems.