Just an observation from reading here.
I interpret it as it going both ways, you can leave whenever you want, or be let go whenever the company wants. No reason needed both ways.
Some people mention being part of a protected class, sure you can’t get fired for being a certain color or race, however no employer is going to outright say that lol they’ll just come up with another, legal reason if they want you gone
You can have seniority and still be let go, seniority doesn’t mean anything