Indeed, TOS 72/2 establishes that the story of Cap's adventure in Greymoor Castle (TOS 69/2-71/2) comes from his memories, but we can't assume that all previous stories were based on his memories. In addition, the synopsis for TOS 72/2 in Official Index for Iron Man states: "After telling the Avengers about his encounter with Cedric Rawlings (TOS #69-71, '65),..." but nothing confirms that he told the Avengers about the stories in issues 63/2-68/2. In the dialog in TOS 72/2, the Avengers only bring up questions about his identity and the explanation he had to give his superiors for his apparent desertion during that particular adventure.
IMHO, if the writers intended to imply that the other stories were also Cap's retelling of the events, they would certainly have not passed the opportunity to use a blurb like "CAP TELLS EVERYTHING ABOUT HIS ORIGIN" or something like that right from the start. And even if that was a last minute editor's decision, they would not have limited the scope of his story to the Avengers the way Stan does at the bottom of the splash in TOS 72/2 when he writes: "...That's why we featured for the past two issues!", which, by the way, is an error on Stan's part because the story spanned over three issues! Of course, the omission does not exclude the possibility that he did relate all those stories to his teammates, but without further proof that he did, that remains only an assumption.
Cap's origin has been retconned over and over, so the authenticity and relevance of TOS 63/2 have been discussed and reviewed in length countless times on several forums including this one. It's probably why MCP has several lines from that issue in its listings. But TOS 64/2 is the only retelling of CAC 1/2. And given that most Golden Age stories are considered as embellished versions of actual events, I would tend to side with the Silver Age version, even if it is told from Cap. I see no reason why he would need to lie or embellish them (your listings do include the stories in TOS 66/2-71/2, after all). And besides, even if those events took place two decades ago for the readers, to Cap, they happened only a few years back because he was in suspended animation for so long. No doubt his memory is still... fresh! Uh-hum!
On a side note, going back to the Index poses a dilemma when it comes to the appearance of Betty Ross. in the character listing for CAC 1/2 in Official Index for Captain America, it clearly says: "Betty Ross (1st, FBI agent)". But in Iron Man Index, TOS 64/2 lists Agent 13 (only app), with a comment that the character was filled by Betty Ross in the original story, but no further clarification. (Thanks Marvel for leaving us in the dark!).
God knows how much I don't want to get into a debate like the one regarding the identity of Agent X-13 in the origin of Cap (Betty Ross, Cynthia Glass, or whoever it was decided after all those retcons, this is still unclear to me, but I digress...). As far as I know, we need to acknowledge the following elements:
- Agent X-13 or Agent R was one of the few people who knew that Steve Rogers was the subject of Operation: Rebirth so it's very likely that she also knew about his double identity.
- Neither Betty Ross nor Agent 13 knows about Cap's double identity in the Sando and Omar story.
- In that story, Betty Ross works FOR the FBI, as she does in many Golden Age stories afterwards, whereas Agent 13 works for the WAC WITH the FBI. Close enough.
- The plot for those women in both versions is just about the same: lady investigates Sando and Omar, nosy girl gets captured, damsel in distress is rescued by Cap and Bucky, the heroes leave the villains in her custody until FBI arrives.
I've only read the Golden Age stories about Betty Ross so I don't know if Silver Age confirms anything about her activities when she was around Captain America and before she took a costumed identity. I can only assume that she was an FBI agent for a while so I can easily accept that she was also Agent 13 in TOS 64/2. I don't want to spoil too much of my fun reading later issues ahead of time so I can't honestly make any enlightened suggestion. I just brought it up to raise a flag, but I'll leave that up to you guys.