My understanding is that up until one year, formula or milk is still the most important part of your LOs diet, so you don't want to be encouraging more solids and less liquids. I would still keep offering the forumla first and the solids second. It's great that he loves his solids, but nutritionally the formula is still the best for him.
Of course your baby's ped is an important resource too, so obviously you don't want to just dismiss their advice. Is there any particular reason they have said to do solids first??