Source? I'm very much in the camp that diet has a huge impact on one's ability to control their eating, but I've never seen anything that suggests that calories in calories out doesn't apply (outside of extremes, like genuine starvation).
So if you drop your intake by 135 calories you may just not walk as much and not even really notice it. Or your body may slow down metabolism a tiny bit, etc.
In my experience (and also studies) change in calorie intake is correlated with change in activity i.e.: when you eat more you naturally move more. Not just exercising and walking but also jittering and cleaning that little bit harder and moving that little bit faster. Or the opposite, saving a little bit of energy.
Instead of moving your whole head to look at something - just a glance and so on.
CICO is still valid but the body adjusts beyond what we can _easily_ measure. It's a lot more complicated but the above is one simple example how it adjusts.