Is autopen a particular sore point in the US for some reason?

Yet you can decide that the secret documents store in your toilet are declassified with a thought?

There's a potential implication that the president wasn't the one making the decisions and they were political favors doled out by unnamed and unaccountable staff. If the president felt strongly about that perception he could've signed them himself. But he seemingly didn't.

The autopen has been widely used without controversy, including by Trump.

The controversy with Biden is that the autopen was allegedly used without the President's knowledge or directive. Nobody has a problem with POTUS's signature getting on a piece of paper without his hand actually holding the pen; that's not the point here.

"Allegedly" is the key word here. Alleged by people who allege a whole lot of untrue things and don't seem to have any evidence for this particular thing.

There is absolutely no evidence it was used without his knowledge.

Did he say that pardons were issued that he did not approve of?

There is not, but right wing propaganda avoids lots of actual news, events and statements because it doesn't look good.

To fill the time there are lots of narratives about non issues without evidence.

I think the conspiracy is that someone pardoned people without Joe Biden's approval right before Trump was inaugurated.

There's a conspiracy theory that Biden wasn't competent enough to sign stuff, at least for some period at the end of his term, with the implication being that none of those presidential acts are valid. Anybody who believes this is mired in an impenetrable misinformation bubble and should be dismissed out of hand.

There’s a conspiracy theory that Biden was secretly competent at the end of his presidency despite public appearances otherwise.

Hey I'm not disagreeing that he was in cognitive decline, but the idea that all executive action should be nullified because of that is crank shit.