No, it's not the depot wearing off, but rather the action from shot he had 12 hours earlier. It's also more noticeable in higher numbers due to too low a dose. Once you finally get tot a good dose for Eddie again, you should start to see flat cycles again. Neko had quite different patterns than Eddie, but if I got a test late in the cycle (like +9) and she was still on her way up at PS, then I knew the insulin was wearing off and her onset number was also going to be higher. If +9 and PS were about the same, or she was dropping into PS, then the earlier test would be more interesting.
Onset is typically around the same time for most cycles. But even once the insulin for that cycle starts to work, it still has some work (time) to take the numbers back down again, especially if there is that rise happening. Yesterday was one example of this, it took a couple hours after onset to get the numbers going down again.