Thickening milk?

Has anyone else heard from their mothers or mother in laws to thicken a bottle before bed for their baby with oatmeal or apple sauce to help keep baby full and not waking though the night? Seems old school? My nearly 5 month old hasn’t tried solid foods yet. I’m waiting for him to double his weight and was planning on skipping the whole rice cereal thing and instead going straight to puréed green vegetables to start. People keep telling me that he’ll sleep for longer once he starts solids since he’ll stay fuller longer. Is there any merit to that? And what do people think about the “milk thickening” thing? My mil said it makes like a milk shake sort of texture and to cut a bottle nipple so it can get through. My pedi hasn’t said anything about recommending this. When I asked she just said that I can start him on solids soon starting with green then yellow then orange veggies followed by fruit.