Today I learned that the WordPress function is_tax() returns false on arc hive pages.
According to the WordPress codex, “You should use is_category() and is_tag() respectively when checking for category and tag archives.”
It appears that a 3rd party developer was implementing some specific code in a post using the is taxonomy function is_tax(“category”, “category-name”) and when trying to do the same on a category archive page just copied and pasted the code and called it a day.
The code didn’t work for the archive page and was left alone for some time. I realized it wasn’t working on the category page and upon investigation learned that the is_tax() function would always return false for a category archive page.