It wasn't about the demographic, but about the fact that their healthcare system would get overloaded, which impacts a lot of treatments for everybody else.
Also the problem with predictions of epidemic is that if you actually do a better job than expected at confinement / protection measures, then predictions are meaningless. You "could have" a lot of bad things happen, but once you do things right, they disappear. That doesn't mean you shouldn't have done those things, it just means that people have been warned properly. He said, if they get hit severely, impact would be much bigger than in the west. He didn't say the 10 million was a done deal.
No virus in history has infected virtually everyone, and there are lots of experts calling foul on that particular assumption right now. It's baked into epidemiological models but those models are always wrong, and the assumption of very high susceptible populations is being floated in several papers as one of the possible reasons.
"This is a huge challenge, we’ve always known the potential for a naturally caused, or intentionally caused, pandemic is one if the few things that could disrupt health systems and economies and cause more than 10 million excess deaths.
This could be particularly if it spreads in areas like sub-Saharan Africa and some Asia, it could be very very dramatic.
We’re doing the constant science to provide the tools to do the diagnosis to provide vaccines, to provide therapeutics and hopefully contain this epidemic, but it’s potentially a very bad situation."
(found this here -> https://www.telegraph.co.uk/news/2020/02/15/coronovirus-bill...)