Does watchdog_feed_events need to be declared as volatile? If so, could you explain why?

It does not have to be volatile if :

• it has a static storage duration and must be read when the function is called from its permanent storage duration. Even if this function is inlined in the ISR handler, the compiler cannot optimize it and keep it in register between the ISR handler vectoring.

The volatile only informs the compiler that the object is side effects prone and it has to be read from its permanent storage before every read and saved after every modification.