My DS started reading at 3.5. He read a mixture of phonics books and Peter and Jane which are look and say books.
He was 5 in the September he started school and by then was reading L6 of Peter and Jane and reading fluently out loud.
He had been at nursery in the school he joined in reception. The nursery teacher knew he was reading and had worked with him each week from when he was 4. This involved covering the early stages and then KS1 sight words (this was about 4 years ago when there were about 50 reception age words) and covering the phonics scheme books to Level 5. Because he then continued into the school with the EYFS profile partly completed, the reception teacher knew where he was up to.
I think he did spend time on the carpet while children covered ah,ah, ah ant, with the actions moving up their arms. In their class they only read to a teacher or TA once a week, but he was quickly moved up to higher levels because at the start of receptionhe was fluently reading Enid Blyton out loud and to himself.
Interestingly, he was both a sight and phonics reader. So he was able to decode new words without any particular problems, but he also read fluntly and speedily, which I think comes once you are also a sight reader. These days I think people are encouraged to learn phonics first and then the sight reading comes a bit later.....but until there is a level of this,needing is very stilted and not fluent. He certainly understood what he read.
I think we got a reasonable experience of reception compared to many. It was partly because his reading ability was already known from nursery, I pressed when I thought there wasn't enough provision for him and they did respond. The big thing that helped him progress though was that he read to us every single night and read to himself too from mid reception - it was one of his favourite leisure activities. I know all schools encourage parents to read every night....it honestly is the thing that makes the biggest difference. It's just too easy to see it as a chore and take days off, especially in the early stages when reading is hard work. By starting quite early, our DS had gone beyond the hard work phase by reception and reading really was enjoyable.
I agree that it's not necessary for many children to read before school, but equally there is no need to delay if they are ready to do it. I think that generally schools are not geared up for it, doubt that children truly can read and are a bit resistant to moving them on. You often do have to push a bit to get proper provision for a child who can already read,and I think they will spend time sitting through very basic stuff. In itself some of that isn't a problem and is probably useful reinforcement as long as they also get stuff to stretch them too.