It's not a prolog, it's a disclaimer, but the warning is unclear.
- "I know this makes me look weird! But keep reading, it is actually not weird at all once you understand the whole story."
- "Before you say it, yes, I already know this story makes me look weird. But I have been framed through the actions of others!"
- "This is such a weird story, you will think I am weird just for re-telling it."
There are a few problems:
Is the author concerned about how the story is received (it only seems weird at first), or their own image (the story is weird, but I am not)?
Meanwhile, the author is almost anonymous, signing with just initials so readers who know what A.B.G. stands for may be able to confirm parts of the story, but readers outside the author's circle will not be able to connect details to anyone specific. Who is the prolog for, a reader who knows nothing about the situation, or a reader who already has an opinion of the author (and this story will shake that opinion)? If the author is anonymizing their name, why be concerned what the reader thinks of them personally? They are not relying on their reputation, and they are distancing themselves from the events.
As a prolog, it doesn't work to make the situation clearer. It's actually a mixed message: "Trust me, I'm going to lie to you" would be a similar mixed-message. Is the author discrediting themselves? Is this already part of the weirdness we should expect?
Consider a similar one-line disclaimer/epigraph by Evelyn Waugh in Brideshead Revisited:
"I am not I; thou art not he or she; they are not they."
At first it seems like a typical "This is a work of fiction…" disclaimer, but it is worded in such an oddly personal way that it appears to specifically address people who will recognize themselves in the novel, and this brings into question the accuracy of the statement as a disclaimer. If he needs to mention it at all, especially to the people who were "there", it probably resembles the truth. So in a way, it works to confirm aspects of the story, rather than deny it.