As a teacher, I know that a lot of what happens to a child OUTSIDE of school plays a huge role on their behavior, performance, etc. DURING school. While home and school are two different environments, one really affects the other.
If a child is prescribed medication - for example, my son has asthma-like symptoms when he gets a cold and we do 2 nebulizer treatments in the AM and two in the PM...neither one would be given DURING school, but they affect his behavior a LOT so it would definitely be something I would want to give his teachers a "heads up" over.
Why do you think it is odd that they ask parents/doctors to report a suspected developmental delay? If teachers are aware that a child has had some difficulties in the past, it can help when it comes to identifying things in the future. Early delays can increase help for a child sooner rather than waiting for them to REALLY struggle and fall REALLY behind.
Again, despite what people think, a lot of factors play a role in a child's school performance and health/safety issues that happen at home and/or prior to a child's school years ARE important and can be helpful information...