Over the next 30 years, population aging is our main entitlements problem and it makes sense to seek solutions that are based on the problem we have, not the problem we want to have.
Beyond 30 years, it is "excess cost growth" in health care that is the main driver of the entitlement deficit. By "the problem we want to have," Biggs refers to the view that we have to worry about health care costs, not demographics. Even if one accepts the view that health care costs are a big problem for Social Security and Medicare, it is odd to imply that the solution is to expand government's involvement in health care.
Regardless of whether you are worried about demographics or the growing use of medical services with high costs and low benefits, raising the future age of eligibility for Social Security and Medicare would be a logical solution.