I don't have experience of the waiver system, but from reading Unlock's information, visas are processed at the embassy, while waivers are processedi in Washington. That's their procedure. While the embassy in London only deals with visas applications from the UK, in Washington they deal with waiver applications from all over the world. I suspect they are much more thorough as well.
Having said that, any new information they have should only be positive. You were given a waiver, travelled to the US and didn't start a crime wave. All those years have passed, and there is no new information on your PNC record, and you have all those extra years of helping people with drug issues. You're helping to reduce crime. I would be horrified if they didn't give you another waiver, but I would be surprised if they didn't make you wait a few months before you get it.
Robert Lightfoot, former head of NASA, said it succinctly in his parting speech in April 2018: Protecting against risk and being safe are not the same thing ... [W]e must move from risk management to risk leadership. From a risk management perspective, the safest place to be is on the ground. From a risk leadership perspective, I believe thats the worst place [we] can be.