Incremental Knowledge
Prophet Muhammad SA was the source of deen. Contents of deen and its understanding are two different things. If someone come up with new contents of deen and claim those are from the Prophet SA we cannot accept it. However if someone come up with a new interpretation of the same ancient contents of deen we can accept it. Thats because the modern understanding of the contents is based on a combined mind power of all those scholars who worked on it since the very beginning and connected the dots based on not only each others work but also in context of scientific discoveries. Some of the historical interpreter of Quran thought the earth was flat so they interpreted some verses as if those were supporting the flat earth belief. The modern interpreters were able to understand those verses much better in the light of new scientific discoveries and established facts. The understanding of Sahaba RA was mainly based on the questions they asked on Quran and not all answers were captured in writing but whatever is available in Ahadiths, all good scholars still refer them and benefit from their understanding and if they have to deviate they have a good reason for that e g the source of narrative is not authentic or it is incomplete, out of context etc.