They claim they went from a 50th percentile to 75th percentile.

https://publications.aap.org/pediatrics/article/149/3/e2021052138/184748/Evidence-Informed-Milestones-for-Developmental

All papers sited were pre 2020.

One example:

https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(18)30003-2/fulltext