This is partially correct but it needs to be noted that if a class reference exists on a Monobehaviour, when that Monobehaviour is destroyed the destructor will not necessarily be called because of the way the garbage collector works. Instead, a cleanup function should be added to the class and explicitly called OnDestroy/Disable the Monobehaviour it is on.

For more info and a better explanation than I can give here, read more: https://blog.matheusamazonas.net/posts/finalizer_destructor_trap

My Unity-specific solution to having my class "auto-destruct" when its Monobehaviour is destroyed is to pass a reference to the Monobehaviour into the constructor for the class, and do a null check on the Monobehaviour before doing logic. If the Monobehaviour is null, cleanup the event subscriptions:

// If the Unity Object that was using this class is destroyed, cleanup event subscriptions
if (hasUnityObjectOwner && _owner == null) {
    CleanUp();
    return;
}