It depends entirely on the type of school. At really top universities and liberal arts colleges, it's very tough to get As in the humanities. (On the other hand, it's not that hard to avoid Cs if you do your work.) Where I went to college, we had no English majors with GPAs over 3.9. Most of the summa grads were in hard sciences. It's not that science was easy; it's that it's possible to learn the material inside out and get perfect scores in science. When it comes to writing humanities papers, nobody could ever be confident that they'd gotten an A. The good students would get mostly A-minus, with a few B+ for when they "screwed up" and a few As that were mostly reserved for when you said something persuasive that the professor had never thought of before.
I'm sympathetic to your point, but I think don't think your categorical condemnation is justified. Grades are far and away the most powerful tool that teachers have to influence their students.
I think the strongest objection to the policy is that it's a hard curve that nobody outside of the class will know about, so it's theoretically possible for multiple students to do work that is truly exceptional, even by the (apparently) high standards of this professor, and yet not be rewarded. That said, an A- isn't the worst thing in the world, and the one A policy will unquestionably get the attention of the students. Depending on the kind of student, it could be a challenge that the students strive to meet.
When I was first teaching English, I would tell my students what the rough breakdown of grades had been on a particularly assignment. There were rarely more than one or two As, but I didn't rule out the possibility of more. This approach has the advantage of making people feel like they might be able to meet my standards without always being shut out of the top prize by a superstar student. On the other hand, there's a very strong subconscious desire on the part of teachers to allow grades to creep throughout the semester. We want our students to feel like they're improving. We want to feel like they're improving too. A one-A policy keeps the teacher honest.
Ultimately I used grades in a totally different way. I stopped giving grades on assignments entirely, and instead gave detailed comments, keeping copies for each assignment for my files. The final "writing grade" for the semester was made up 2 grades: one for the absolute quality of the final paper, and one for the quality of the student's effort to improve over the course of the semester. For example, a student would lose points for consistently making the same types of errors. Students who responded to commentary did better.
What I found was that not having any grades during the semester made the students very uneasy. They were forced to read the comments carefully instead of just going to the last page to see what the grade was. I also found that my office hours were suddenly jam-packed, because students wanted to make sure that they really understood what was being asked of them.