I have a July born ds. He was my first and I poured love and attention into him.
But he had developmental delay and ASD. He didn't walk until 2.5 years and didn't talk until 3. At the time you could not defer. The only choice was sending a year late into year 1 which would have been disastrous.
So I sent my just 4 year old, barely verbal son to school. He had no clue what was going on, he couldn't really dress himself. No idea of letters. He could recite numbers but didn't really have an idea of numbers.
They started him off writing. He couldn't write at all really for 3 years, but he tried hard. Turns out he has bad dyspraxia and due to being started off to early writing has developed a thumb wrap grip which is dysfunctional and we can't really change change now, so he will never write well.
He's always been socially a bit behind his peers and naturally gravitated to similar summer born boys.
He worked hard and we worked hard and we managed to get him from below expectations in all areas up to meeting expectations. Tried the Kent test, failed by 14 marks. I looked round lots of other schools but the provision for him was not great. So with family financial help we have scraped together and sent him to private school. I put him back into year 6 in the junior school so that he is now eldest in his year, rather than youngest. He is doing really well and I am phenomenally proud of him.
But I'm very angry he had to start when he did. He has always had to struggle. He has always known he is behind his peers. I firmly believe he could have passed the Kent test the next year, which would have saved us 100k +
But you can defer now! Statistically summer borns are disadvantaged academically. Boys more than girls because they mature later anyway, so asking a just turned 4 boy to sit down and pay attention is more of an ask that a just turned 4 girl (in general). But you can monitor your child, see if she is ready and defer if not. I personally would have defer as the default position, rather than the other way around, but that is my personal experience at play.
Not sure why deferring is seen as a 'pushy parent' option. It just seems like good parenting to me to make a choice that would lessen your child's struggle.