Yes, and what you're reading into the text.
We know what Jesus told Peter, and He didn't say anything about the sufficiency of the cross, that I can recall.
But He did say to Peter (Peter was
definitely there when this happened) after He Luke 22:19 "took bread, and gave thanks, and brake it, and gave unto them," said, "This is my body which is given for you".
This Jesus says in the context of that Peter is
right there and that Jesus had already been preaching to Peter----bluntly----His looming 'DBR' (death burial and Resurrection).
In this context, "20 Likewise also the cup after supper, saying, 'This cup is the new testament in my blood, which is shed for you.'"
Jesus was not just preaching the (then future) events of the 'DBR' to His (then future) Apostles, but also at the Last Supper, the meaning and the eternal significance of "Paul's Gospel to the Uncircumcision." Communion is a remembrance of the one Gospel's, New and eternal Covenant's, eternal implications. "My body which is given for you"
Paul's Gospel 1st Corinthians 15:3 " For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;"
That's literally Paul telling the Corinthians what
Communion means; when He said "This is My body", He was talking about the 'DBR'; and all of the other Apostles knew the same thing too, it just took Paul to do part of the last bit of persuasion in order to completely reveal to them all exactly what Jesus Christ had been trying to teach them all along.
Actually, there was quite a crowd of Jews there with Peter doing exactly what Peter was doing....compelling the gentiles to get circumcised or stay separate. Peter by his silence, perhaps, but,
That's an argument from silence then. So that idea that Peter was teaching circumcision, doesn't have any support from the Scripture.
nevertheless putting pressure on the gentiles to keep the law in order to be saved.
Yeah, perhaps. Not impossible. But also, doesn't necessarily require that MAD is right, even if it definitely is true.
Paul had already expounded his gospel to Peter, so, of course he knew.
I believe that's basically why the other Apostles knew that Paul was the legit replacement for Judas, the "chosen vessel" not the man who won a dice-throw. Paul expounded the 'DBR' to them; Matthias didn't do that.