But the same morals and 'ethical guideposts' apply throughout, do they not?

By way logic does a libertarian say that e.g. government coercing people to obey quarantines is acceptable, but that the government coercing people to pay for cheap public preventive care (before expensive specialist treatments become necessary) is not?

Quarantine prevents others from getting sick, while preventative care only prevents you from getting sick.

For comparison, compare laws against punching other people to laws against punching yourself.

And if you prevent someone from getting sick via preventable care you prevent them from spreading that sickness to others. Additionally even non-communicable diseases often have large impacts on those related to the person with the disease, so I don't see how you can truly separate the logic.