I consider myself largely AP and I did child led "training."
Quotes are there because I don't believe the process should involve any kind of parental influence but rather should be a natural discovery each individual child makes for themselves.
My daughter was 2 1/2 when the thought process kicked in. She asked for a potty seat because she told me she didn't want to poop in her diapers anymore. I told her that when she sorted out when to tell me she had to go *before* she went I'd sure get her one. Delivered factually, zero emotion on my part because I could have cared less if she could manage the skill at that point or not. She thought on it about a week and then one day SNAP - immediately started telling me every single time she needed to go, before she went, and never had a single accident after that, pee or poo, day or night.
My son was 3 1/4ish and one day he asked for underwear. I told him the same thing. Tell me before you need to go, keeping diapers dry, and you can sure get underwear. No big deal either way, just let me know when you can and you're ready. He stopped literally overnight and never had a single accident, pee or poo, day or night. We went and choose underwear for him and that was that.
No pressure. No tricks. No boastful pride. No manipulation. No shame. No bribes.
Although I'm sure it won't be a popular opinion here I don't believe in EC (studies have shown withholding voiding at a young age can be harmful to still developing internal organs so I don't believe that should be encouraged via EC or "training" processes). Nor do I believe that M&M's, sticker charts and promises of toys should be used to bribe a child into mastering a personal process.
I insisted on using the same approach with all of my daycare and foster kiddos and it's the only approach I've seen work 100% of the time, with 100% of kids, all under the age of 4, permanently with zero regression and with nothing but a huge boost for the individual's psyche (as long as intentional or unintentional language isn't used in tandem - labeling diapers as "for babies" and underwear for "big boys/girls" for example.....lots of kids have plenty of reasons they want to remain the baby, or have a fear being a big boy/girl so junk like that is just counter-productive). It should remain completely a non-issue to you as the parent/caregiver because it's not about you. The only prompting I offered while picking out that green potty seat with decorative stickers and those first Thomas underwear was "are you proud of yourself?" and when they both answered YES, I told them I was so happy for them for that
In short, there's no such thing in waiting too long if the child hasn't gotten there themselves yet