I won’t give away many spoilers here, just in case you want to play this earnestly, but aria-hidden="true" being focusable while also not being available in the accessibility tree should be a warning in itself to be careful with <button> elements. Using aria-hidden="true" on a <button> creates a trap for keyboard-using screen reader users.
Buttons are so frequently abused on the web. My mind immediately goes to applying a disabled attribute with no added contextual information as to why it’s disabled. At least articles like this can help you understand the plethora of foot guns that can be caused both by attribute misuse and CSS misuse.