There is some gap between AGI and a singularity, at least in principle. The term "singularity" doesn't mean "black swan that disrupts society", it means "intelligence trends to ~infinity (or at least something incomprehensible to humans) recursively in a very short period of time". That's (on paper) a much stronger result than an AI that can reason as well as humans in a domain-general way.
An AGI that is 20% better than humans at everything might be able to recursively improve itself effectively without limit, but it also might not. It took billions of humans millennia to invent things smarter than ourselves even in limited domains; such an AGI - even if it is significantly smarter than humans at everything - might take decades or centuries to produce a similar relative improvement. No doubt it would still change our world in massive ways, but it wouldn't be a singularity.
An AGI that is 20% better than humans at everything might be able to recursively improve itself effectively without limit, but it also might not. It took billions of humans millennia to invent things smarter than ourselves even in limited domains; such an AGI - even if it is significantly smarter than humans at everything - might take decades or centuries to produce a similar relative improvement. No doubt it would still change our world in massive ways, but it wouldn't be a singularity.