People making arbitrary rules about when they think "readiness" is ("They're not READY until they can wait 15 minutes/wait half an hour/pull their tights up by themselves/wipe their own bum/locate the nearest toilet via signage/whatever"), and insisting that anyone who doesn't wait that long is WRONG, are extremely irritating.
I'll give an analogy. I live in a place where we tend to meet lots of parents from all over the world. I was a bit struck by the fact that some mums from one particular part of the world tended to spoonfeed their children pureed food and give them bottles (rather than shifting to a cup) until what I considered to be a really advanced age.
When they saw my older baby drinking from a cup and feeding herself stuff, they were shocked. "But.... she'll drop things?" "Aren't you worried about spills?"
I don't mean that they were cynically chuckling "To hell with my child's development, I'd rather have an easy life and save myself from wiping the floor, bwahahah!"
I mean that these mothers took spills and drops and needing-help-with-certain-foods, as a sign that the child was NOT READY for self-feeding or cup-drinking, and seemed to feel that this was somehow not developmentally appropriate yet.
Of course, it made things easier for themless mess, less clearing up. On the other hand, they had to try and accustom stubborn older toddlers to feeding themselves and take their precious bottles away at some point, and it was often a big battle by then-just like the battles I've seen when parents try to toilet train some preschoolers, some of whom start withholding poo and getting constipated because they are very very used to nappies by this point.
Or, to give a counter example, I did not have the time or energy to take my children to swimming lessons when they were very little---we have no car and are not located near a pool. So we waited till they were about 7 and then did a crash course and they learned very quickly. But that doesn't mean that "Children aren't READY to learn to swim until they are about 7 and can do it in a few weeks!" It is fine and actually a wonderful thing to start toddler swimming lessons and do it gradually from an early age, if you have the time and motivation to do that.