You are eating less, but high insulin is telling your body to store
You held the deficit. You weighed the oats, you logged the days, and you did it for long enough that it should have shown by now. The part that gets left out is what insulin is doing while you do all of that. When insulin runs high, your body leans toward storing what you eat rather than burning it, and it keeps asking for fuel even after a meal that was plenty. That is why you are hungry again an hour after lunch on days you ate enough.
Hunger an hour after a full lunch is one of the clearest signs insulin is running high.