Hi VS, I'll give my (sorry long) story of why we weaned early. Around eighteen weeks.
As you requested, and because I agree with your point I will say you should not wean early without very close supervision from a medical professional, ie dietician/ paediatrician etc. You should also feel confident to cite the guidelines to them and feel happy with their replies before you begin early weaning.
DS2 was born a healthy 8lb at 42 weeks. I began breastfeeding (as I had DS1) and left hospital happy with how things were going. After two days it quickly became apparent there was a problem. This was put down to a tongue tie, unfortunately in our area these were not routinely corrected.
I did have alot of breastfeeding help from a very lovely midwive but eventually had to stop and start expressing etc. DS2 for an unknown (at that time) reason was unable to suck from a bottle as well. The feed would come down his nose and he also sufferred from reflux. In short we were in feeding hell. We had to feed all of his feeds via a cup or syringe. After four weeks I was mixed feeding and after eight formula only.
At twelve weeks after numerous chest infections he was admitted to hospital with bronchillitus. He was tube fed and was very ill. When we returned home we continued as before but now with inhalers etc.
He was admitted to hospital several more times untill eventually seriously ill with pnuemonia at seventeen/ eighteen weeks. As he was so thin (on 0.2nd centile) and so ill he was tested for cystic fibrosis and many other life limiting illnesses. Thankfully they were all negative. It was at this time we were advised by the hospital dietician and all of his medical team that early weaning alongside high calorie milk was necessary. We followed a particular diet that basically consisted of very high calorie meals. For the first fortnight of this he was in hospital and we were closely monitored.
For my baby he was in a cycle of not having the energy to suck, therfore not gaining weight, therfore not having the energy to suck etc etc.
He did start to gain weight and last year when he was four he was diagnosed with di-georges syndrome, which is a chromosome abnormality. We also found that for him it means a type of cleft palate, a comprimised immune system, poor hearing amongst other less serious things. Tbh it was a relief to get a diagnosis as I had always felt guilty about his chest problems possibly being down to stopping breast feeding, I now know that for him it was pre determined, before he was even born.
He is now settled on the twelvth centile and he follows a normal diet. His medication has been sorted and three weeks ago he had his palate repaired. I hope we haven't caused him any problems with his gut by weaning slightly earlier but firmly believe that it would have been more detrimental to not have iyswim.