I wonder if that 55% is from mturk or other survey sites that can be somewhat questionable in terms of quality with how much people are paying attention versus maximizing their hourly survey earnings.

It says on a similar test - it's a reference to a different study with a different data set.

The humans are probably overthinking it. You get ~55% by assuming by answering "Biden" for everybody.

In fact, the dating site dataset was ~54% conservative according to their explanations of included data, but the point stands.

According to Wikipedia only 51.3% voted for Biden/Harris.

The dataset was not restricted to voters.

Do you have data that includes non-voters? I haven't seen any; most polls are limited to voters.

There were tons of national polls done for Trump's approval that included all adults (instead of likely or registered voters). Trump fared noticeably worse in the polls of all adults throughout his presidency.

Approval isn't the same thing as preference among two choices. Trump received a considerably higher percentage of votes than his approval rating.