In Texas you don't need reasons to fire someone.
Or to put it another way: just because you can fire someone by rolling dice doesn't mean you can fire someone for being black.
That's part of why you'd often see lots of HR bureaucracy regarding firing process, documenting infractions, performance improvement plans, etc also in states where technically you can be fired without a reason.
They're trying to avoid paying out unemployment by saying he failed to show up for a shift but even sans-COVID firing after one absence is abnormal.