I can see the point now. Does make sense. It was announced as a feature and I recall back then I was happy because:
- I was new and was just unlocking disks, so it was frustrating not to be able to use them right away.
- It was counter-intuitive that you had to go and update defense for them to show up, it was often forgotten for weeks.
Maybe the feature should be tweaked to prevent the abuse you mentioned but still allow some leeway for newer players? E.g. all your war/arena/coliseum defenses pick up your new disks on the start of the day.