[orra]

Of course it's reasonable to use cat on one file. Why should it work for all 𝑛≥2 files, but suddenly fail at 𝑛=1?

Despite the dismissive tone of the article you linked, if the overhead of one single process was remotely relevant, shell wouldn't be a good fit.

[benatkin]

Yes, it should and does work for 1. That doesn't mean it's a good use of cat.