I confess I hadn’t paid enough attention to catch the difference.

Public option = choice of government provided healthcare or private insurance

Medicare for All = no choice but government provided healthcare

I suppose the MFA strategy is that for it to work there needs to be the entire population paying into it. I expect that given enough time the public option would easily become preferred by enough to be viable.

The bugaboo would be in the transition.
“You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.”
– R. Buckminster Fuller