Found one more, hopefully not a big deal. Just like the first one, AND and OR produce identical query, only correct for AND.
$this->model->books->findBy([
ICollection::OR,
['title' => 'Book 1'],
[ICollection::AND, new NoneAggregator, 'tags->id' => 3],
]);
$this->model->books->findBy([
ICollection::AND,
['title' => 'Book 1'],
[ICollection::AND, new NoneAggregator, 'tags->id' => 3],
]);