Was it a secret? You could have guessed that something advertised [0] for "AI" had some kind of SIMD. Even ChatGPT 3.5 can give relevant code to use "AI" features [1].

0: https://www.espressif.com/en/products/socs/esp32-s3

1: https://chat.openai.com/share/3e1f990d-e8eb-4e56-acbb-ad5a33...