Yea I've known plenty of people with performance issues that were let go as soon as HR found some technicality to pin them on. One left a guest unattended at the office during lunch for 15 minutes and they fired him for it the following week

I doubt that simply because they gave everyone they didn't fire who did it an official talking to. It's atypical for a BigCo to do that if they're simply manufacturing a pretext.

the article seemed pretty clear:

The staff who were let go routinely misused their vouchers, while others who misapplied them less frequently, were reprimanded but not fired.

Do they though? You're an at-will employee. Unless there is a contract, you can be fired for any reason including cutting costs. Just like you can quit whenever. Wrongful termination lawsuit happen when employ fires employee for illegal reasons(gender, sexual orientation, race, religion, or disability status).

It's hard to prove intent, but convincing a jury there's a pattern of discrimination is a lower bar. So perceptions matter.

Doing things by the book provides evidence that the process is fair, objective, and was reviewed by multiple people.

In California, yes. It's trickier to fire someone due to the labor laws. It's not as strict as EU, but typically requires performance reviews and advance notification.

To fire someone in CA who does not have bad performance reviews, it much easier to find some other infraction as justification.

Here's a random guide found on google: https://www.jibble.io/labor-laws/us-state-labor-laws/califor...