Are you not looking at the facts of this specific case? The restrictions being enforced were literally ending in an amount of time equating to a long layover.

Japanese immigration officials, like the overwhelming majority around the world, have wide latitude under law to exercise discretion.

It's well documented in the work of the small army of legal professionals employed to battle Japanese immigration's barely disguised rapidly xenophobic treatment of all foreign travelers. A hatred of the "filthy gaigin" only inflamed by Covid to an extent unmatched by any country in the world.

If indeed you've encountered "spiteful" US immigration officials, were you actually deported? Could they have? I presume if they were "spiteful", something about you paperwork wasn't in perfect order and yet, you almost certainly weren't deported.

Deportation in practice is reserved for egregious cases, not simple errors and certainly not in a case where common sense would prevail at one of the numerous levels of review that would take place before you were forced back into a plane.

There is simply no comparison. Japanese officials stand alone as uniquely contemptuous of foreigners, it's no secret, it's very long standing, it's not limited to a handful of bad apples, and there's no denying it.