This is about social security and has nothing to with health care.
In fact it says:
"Although the agreement between the United States and Germany allows the Social Security Administration to count your German credits to help you qualify for U.S. retirement, disability or survivor benefits, the agreement doesn’t cover Medicare benefits. As a result, we cannot count your credits in Germany to establish entitlement to free Medicare hospital insurance."
Comments
Doesn't matter. Even if you are a German citizen and by 55 you've never been in the health system you're out of luck.
In the above described scenario (US-based retiree moving to Germany), its likely the social security totalization treaty applies, giving them access to the health system: https://www.ssa.gov/international/Agreement_Pamphlets/german...
This is about social security and has nothing to with health care.
In fact it says:
"Although the agreement between the United States and Germany allows the Social Security Administration to count your German credits to help you qualify for U.S. retirement, disability or survivor benefits, the agreement doesn’t cover Medicare benefits. As a result, we cannot count your credits in Germany to establish entitlement to free Medicare hospital insurance."
There might be other loopholes though.
It appears that if an immigrant was previously in a public health care system in their country of origin, they would qualify:
https://www.tk.de/firmenkunden/versicherung/tk-service-ausla...
https://www.krankenkassen.de/incoming/leben/nicht-erwerbstae...
That would cover most EU countries, though probably not the US (assuming that "private, but mandatory" does not qualify as "public").