She did a peer-reviewed deep dive into the test design documentation [0] Stated in the second sentence of this article with the link.

Where she found:

>> According to policies buried in the documentation, the agency administering the tests adjusted their difficulty level every year.

She goes on to say that difficultly is increased. As shown in my original quotes of the article above.

I have not read her paper or the test design documents; but it appears she has and that she does have the evidence.

[0] https://doi.org/10.1080/15427587.2024.2415618