I have read the article on a FB page. Its a particular algae on the south west coast what is more common in Ireland. The dry verge is not adequate but you usually find algae on the North and East side what lacks sun and on new builds with very good insulation.
The manufacturers are having to reduce the biocide in the material so that doesn’t help either. Applying a sealer wont stop it but it will be easier to clean off sealed render.
There is a market there for cleaning it off. But it will be back.