breast milk is actually a wee bit more calorific than formula
formula is 'heavier' therefore fills a baby more, so can seem more satisfying, but just it takes longer to digest than BM
a good breast feed or a good formula feed is larger in volume than a spoon or two of baby rice or pureed carrot, the majority of which will be pushed out , scraped off the chin,back in, and out, and in etc !!!
so it is more filling to give milk
there are frequent growth spurts in a young baby, which give rise to the notion that milk is no longer satisfying at 12 weeks/ 16 weeks/ 20 weeks
you can do no harm by delaying weaning until 6 months
your baby will show signs of readiness, loss of tongue thrust reflex being a good one, waking up in the night and seeming hungry or chewing things are not neccesarily indicators that food is required
babies don;t know food exists, so they are not missing out