I'll say it again "end of quote" is
LITERALLY WHAT YOU ARE SUPPOSED TO SAY
at the end of a quote.
And as far as him also saying "repeat the line", Biden used similar phrases about repetition for emphasis 6 other times in that same speech, including ‘let me be clear,’ and ‘let me say that again' before saying it again.
If you are looking for Joe Biden speech gaffes and glitches there is plenty of meat on that bone to talk about. But what you're talking about right here is a nothing burger.