I have also submitted a bug report for this exact same issue that was not present at the beginning of September 2024.
Before this time, I recall the profession trainer having ONLY the Available filter on by default.
Both the Unavailable and Trained were unchecked by default. If I had desired to see any of those lists, it would display them as desired and when I talked with the profession trainer again, the behavior would be as it was from the start as described herein.
Please examine this easy-to-fix defect and release a deployment into Production for the players soon, Blizzard.