Western thinking tends to promote agency while royal or kingdom thinking promotes representation. Royal/kingdom thinking is higher-level thinking.
We know, functionally, the bread and the wine are not the flesh and blood of Jesus or any man for that matter.
But Jesus was speaking from a royal position. In such a position, a thing represents what He says it represents.
Now, a certain thing doesn't have to function like the thing it represents (like a lamb can never be a man). So Jesus wasn't talking about the agency of the thing. He was talking about what a certain thing was in representation.
So later we read this from the same Jesus who spoke in John 6:
And as they were eating, Jesus took bread, blessed and broke it, and gave it to the disciples and said, “Take, eat; this is My body.”
27 Then He took the cup, and gave thanks, and gave it to them, saying, “Drink from it, all of you. 28 For this is My blood of the new covenant, which is shed for many for the remission of sins.
So it's quite clear that the bread and the wine were not functionally like the body and blood of Jesus YET Jesus said about the bread "this is my body" and about the wine "this is my blood".
Does Jesus have the authority to say that the bread and blood represent something other than bread and blood?
If you believe His words here:
"And Jesus came and spoke to them, saying, “All authority has been given to Me in heaven and on earth."
Then you would have to conclude that He can has the authority to say that the bread and wine represent whatever He wishes they represent. This is royal thinking.
The bonus for us is: we are allowed to participate in this higher-level thinking. So, when we eat the bread and drink the wine and agree with Him that they are in fact his flesh and His blood (while not functionally so) we fulfill the requirements of His word spoken in John 6:
"Unless you eat the flesh of the Son of man, and drink His blood, you have no life in you."
The benefits of this, like all things of eternal substance, are only obtained by faith. That is another thread.