Ahh....perseverance of the saints!
You’re not proving your case here GCC. John 6 really deals less with ‘understanding’ and more with ‘accepting’. To Peter’s credit, the the HS hadn’t yet done His work at Pentecost....yet Peter accepted Chrsit’s statement through the preserving power of the Lord.
But had Christ explained what it meant, there really would not have been anything of significance to accept. What was it about this statement that was so problematic, much more than the comparisons to the vine, the door, the good shepherd, the gate, the path and the like that it required St. Peter and the other Apostles to accept it contrary to both reason and the Jewish Scripture?