How would you even begin to prove something like that? No exec would be dumb enough to send an email that says "we see that the bottom 11% in your organization is mostly marginalized groups, we can't let you fire them". It will be a wink-wink nudge-nudge during a 1-1 meeting.

"As you all know, we are committed to becoming an Anti-Racist/Anti-Oppression company. Layoffs like this can have a more pronounced impact on marginalized communities, so we were particularly focused on ensuring our layoffs – while a business necessity today – were carried out through an Anti-Racist/Anti-Oppression lens."

Any one who isn't asleep at the wheel is well aware that corporate/institutional newspeak terms like "Anti-Racist/Anti-Oppression lens" means anti white and asian.

IANAL, but, it'd be tough for sure. You'd need to compare who was fired to who wasn't and contextualize with metrics that made it clear it wasn't coincidence.

The legal process itself opens the door to proving it. You sue them, and if you survive a motion to dismiss among probably some others, you’ll get to go into discovery.

Title VII prohibits employment discrimination based on race, color, religion, sex and national origin.

If 90% of the people who work at Twilio are white, and 90% of the laid off people are white, that isn't discrimination.

If the decision to fire is based on the demographic makeup rather than the individual's performance, it would still be discrimination (in a purely ethical sense)