I found it odd that they'd publish such a poor track record, so I checked the worst performing position ALLK (-97%). The stock was at 100-ish in December 2019 (their reference), and today it is at 3.22.

Consequently, it seems that the performance that they are reporting is that of the stock, not of their short.

Edit: fixed the reference date.

It's highlighting just the opposite - that their short calls are prescient. You're seeing it's all negative because they are betting that those stocks will drop.

I didn’t follow that at all. That page shows the change in stock price for the companies, not the unrealized gain/loss from short positions. That doesn’t tell us how their portfolio has performed, but it suggests they have a good track record of calling losers. What am I missing?

Those aren't negative results on 'short positions', they're the underlying, i.e. taking the short position was a good call. '[Every] single short position is turning a profit'.

I'd agree that's confusing/ambiguous if it weren't for the S&P comparison. ('If we'd taken an equally valued long position in the S&P 500 instead' would be a weird thing to state.)

That's exactly how you profit from a short position.

The "Big Short" was negative until the market caught up.