Yes that is true, scary mum
. And in other sports too. In rugby union it is possible to make a very real comparison because in New Zealand junior teams are categorised by size and weight rather than age, and there the discrepancies around birth-month are much less pronounced.
Tennis in this country now has split seasons so new age groups are done every 6 months rather than every year and there are already early signs that this is leading to a more even spread of results as children who are young in their year during the summer season will be old in the winter season.
Apologies for the digression into sport – it’s the sole area in which I have any expert knowledge
– but if physical maturity makes such a big difference it seems logical to at least ask the question whether mental maturity does too.