Hi, Traverse,
In my opinion, while you may have, ‘… thought about this before…’ it needs to come off the ‘back burner’ as you give this even more thought. Your post seems to be based more on ‘feeling’. For example:
This is a good point and one I have thought about before. My initial feeling is because even though they did not understand they knew Christ had “the words of eternal life.” In the end it seems they would understand when communion is first instituted.
I am really not sure about what you mean by, ‘…in the end…they would understand…’. Recall that these Jews had eaten the bread and fish that Jesus had miracously given them the day before. They people had seen the Power of God - and sought out Jesus - to get another free meal! They even begin their greeting to Christ with an insult!!

Their hearts were far from following Christ when He chalenged them.
If someone told you some bread was their body while they were in the room with you you’d understand it as symbolic and not literal by the pure fact that you are looking at this man talking about something that is clearly bread. They would not have anything to be confused about then.
I think what is important is that Eucharist Discourse in John 6 comes towards the end of Christ’s Public Ministery - no one gets 5,000+ people to follow them in a desert just for the thrill of it. The people who followed Christ were basically aware that He was very Special, could cure illness, raise the dead and taught like no one else did - by His Own Authority. This isn’t ‘someone’ - but Christ Who is talking to these people. While you may have dismissed the context with your analogy - it is quite real. The same Someone Who died that we may live eternally with Him - is the same Someone Who declared that unless we eat His Flesh we have no life.
But I digress, in all honesty part of this may very well be semantics because I’m aware that the catholic belief (unless I am mistaken) is that they are literally the body and blood while retaining the physical appearance. That is, it’s a spiritual transformation. I believe that we partake on a spiritual basis as well so this may very well be a semantics issue.
I really could not disagree more. Christ says unless we eat His Flesh and drink His Blood we are dead - and you dismiss this as semantics?

Seriously, even free-meal motivated Jews understood Christ to say that they had to EAT (as in grind and chew) His Flesh. The understood this was no analogy, they understood He was calling them to a higher level of understanding (remember, He told them that their fleshly thoughts profited them nothing) and they REJECTED CHRIST! This is the only time there was a rejection of Christ based on doctrine.
What I have always marveled at is that Protestants believe that God created all out of nothing. No argument - after all He Is God! He did not have to do this - He just said it and it was done.

These same Protestants believe that Christ died to save us from Hell. No argument - after all He is God! And, again, He just said it and it was done! But, when it comes to giving us His Body, Blood, Human Soul and Divinity under the appearance of Bread and Wine - ooooooooooo now that’s another story!

He can’t DO that!! He did not SAY that!! And, the only way around this is to claim this is just semantics. Honest, such an argument simply makes no sense if one truly believes John 6 and the Words of Christ as recorded by the Synoptics at the Last Supper - and this is from a group that generally claims ‘Sola Scruptura’!!
So, let’s discuss this. And, when it comes to the Early Chruch Fathers - NONE OF THEM ever said the Eucharist was just symbolic, was a semantics game or somehow is a deception. They believe - as the Catholic Church believes today - that once the words of Consecration are said, then the reality of what we see as common bread and wine has totally changed.
God bless