My weight goes up and down by some 10% every couple of years, I cycle and run (ultramaraphons) and climb and more, and I track and analyse both food and spending with common tools and myself. Which is why I am acutely aware of how at least my body behaves in this respect. And I see people around me who do similar things.

Your point seems to be based on the idea that if it is 5%, it is the same as zero, because metabolism compensates (?). I do not know if this is the case at all or if this is relevant enough to change this 5% number. If this is the case, it is a factor, but it is something peculiar.

Instead, I find, that while a single 10hr trail run spends days worth energy of usual activities, several 5% factors each day, which grow from habits like brooming or taking a walk instead of taking a bus, quickly exceed, or at least strongly contribute to, extreme individual spendings. Also while a long event seems to cause immediate weight loss, it is almost entirely water. So it is a bit hard for me to believe these small spendings are zero. In fact, I find that people often underestimate how simple habits change weekly calorie spending. At least for me, these things make much of a difference in the weight change.

And yes, I have some brooms, and I broom for some 15min a day probably, plus maybe 1h per week.