Classic command course discussion stuff...do you elevate even slightly the risk to the many to reduce risk/save the life of one?
The patient was receiving attention from a medic and was going to do so throughout the landing..
I'm not sure what the crew/door config was on this flight but it is possible on BA Airbuses that the Cabin manager would be the only cabin crew member covering the forward doors, the rest of the cabin crew are elsewhere.
As you say it requires a careful risk assesment....