I was told on an NCT weaning course that milk should be their primary source of food as nothing else rivals the nutrition. So if you fill them up on something else then offer them milk they are losing out.
NCT information is not wrong but it is incomplete. It is 100% correct that at the start of weaning babies should get most of their calories from milk. Milk remains an important source of fats and calcium throughout first years of babies life.
At the same time, between 6 to 9 months, solids become important for cognitive development since they are the primary source of iron and other essential elements:
www.who.int/nutrition/publications/guiding_principles_compfeeding_breastfed.pdf
Page 22 of the WHO booklet:
At 9-11 months of age, for example, the proportion of the Recommended Nutrient Intake that needs to be supplied by complementary foods is 97% for iron, 86% for zinc, 81% for phosphorus, 76% for magnesium, 73% for sodium and 72% for calcium (Dewey, 2001).
For whatever reason, some weaning advisors happen to ignore this particular part of WHO guidelines. The catchy phrase "food before one is just for one" has nothing to do with WHO recommendations.
I have also introduced all the solids meals one hour after milk but between 8 and 12 months I made an effort to offer DD more solids and a bit less milk.