My "ages 2 and up" programs are full of 2 year olds with barely a 3 or 4 year old in sight.
And they are very NEW 2 year olds--26 months as opposed to 34 months.
Wild, wiggly, still learning to sit down for a few minutes, the minimal attention span sort of 2 year olds.
Plus several toddler siblings whose parents/caregivers don't want to corral them. So they wander around and distract the "big" kids even more.
It's making for some interesting storytimes, I'll tell you that......