No, this isn't a thing anymore. If may have happened many years ago (as some people said, there use to be September, January and April intakes in some areas so things were a bit more flexible). It doesn't happen any more though and with good reason. September babies are statistically at an advantage, academically. While some might be ok starting a year early at 4, it could become very apparent the difference in their maturity over the next few years, compared to their peers who are all older. This would then put them at a disadvantage. Why would you want to do that? It's socially alienating too as they get older. They won't be allowed to play in the same sports team as their classmates, they'll learn to drive later, they won't be able to legally drink until after finishing their A Levels, while their peers are starting to go out legally celebrating in pubs and clubs throughout their final year of sixth form etc.
Summer born deferral is an option to support those who may need it, so they are not disadvantaged by being the youngest in their year group. It would be madness to choose to put your child, who is even younger than children who can defer, in that position.
Sometimes autumn born children do stand out at pre-school, as they are usually naturally more mature than their peers who are up to 11 months younger. That isn't a reason to push them forward to be with peers up to 12 months older though.
A good pre-school and Reception class will make adaptations to ensure your September born isn't bored if they are strong academically (the same as they would for any child born in any month if they were particularly talented in certain areas). Being ahead academically does not automatically mean a child is ready to skip a whole year group though. Also, a child who is academically ahead at 4 won't necessarily always stay ahead (especially if they suddenly become the youngest in the class). Their younger peers often begin to close the gap as they grow older and more mature. Autumn born children can sometimes struggle with this switch in dynamics, if they're always use to being 'the best' and then they suddenly have several peers achieving at the same level, or perhaps even higher, one day.
All children are different. Some children in Reception can already read, are good with numbers and are picking up writing well, but they might lack resilience and struggle to regulate their emotions. These are their personal targets which they need to working. They are not emotionally ready for Year 1 yet. There may be other children who are far more mature, but struggle a bit more with the academic subjects. They're all different and all have different targets regardless of the month they were born.
Give your September born the best start to their education by having them enter formal education at nearly 5, as opposed to not quite 4. Not that it's your choice anyway though. As I said, it's not a thing to start September born children early now.