Presumably these Cloudflare HR employees do have the data for why this person was laid off, and they might even have it in front of them, but yeah legally they can't give them any more specifics.

As far as I'm aware, evidence of good performance could be used to strengthen their case to collect unemployment (if Cloudflare tries to fight Brittany's unemployment claim); it could also be used as evidence in a discrimination lawsuit. But given that Brittany said that many other team members also got invited to 15 minute calls with HR, there's good evidence that CF didn't discriminate, but it's also evidence that this could've been a mass, quiet layoff.

Although it sounds like the simple fact that her clients backed out at the last minute could be enough evidence for poor performance, even if the sales were entirely managed properly before that point.