Most boys absolutely cannot retract by age 3.
If you read non US books on urology, you will find that "most boys can retract by age 3" is correct. When discussing foreskins, one should always avoid any US based documents because if old enough, are from pro-circ era, and if too recent, are written by anti circer activists.
You are affraid that if one accepts that most can retract by 3, that any boy who can't by 3 will be circumcised. This is a false argument. Say you set 18 as the arbritrary age where a non retractible foreskin becomes diagnosed as a true phimosis. This does not change from thet fact that many boys will have retractive foreskins well before that, and that as soon as part of the glans can be exposed, that part needs to be rinsed every day to preent infections, and strecth foreksin to prevent acquired phimosis. And as things progress, more and more of glans can easily be exposed and runsed every day.
Note that in France and Québec in the 1960s and 1970s, the age of 10 was common to diagnoze phimosis and prescribe circumcision. (it is one reason that in Québec, long foresins were rare for teen and adults since lopng foreisins had greater odds of not being retractible by 10).
One can argue about what age a phimosis can be diagnozed. Whether 10, 16, 18 or 25 doesn't change the fact that most males will have retractive foreskins well before that and that cleaning ritiual needs to start very early to expose whatever portion of glans can easily be exposed to rinse it.
The "do not retract" anti circ propaganda is a recipe to not oncluy increase infection rates, but also help convert normal congenital phimopsis into permanent phimosis which means by adulthood, the guy still has long unretractable foreskin. As long as your foreksion cannot retract during erection, it will grow legthwise and not need to retract during erection instead of being stretched diametre-wise to eventually become retractive.