two points,
firstly, the safety digest is full of one eyed opinions from others in industry looking to have their moment in the sun. It is a very long bow to suggest that becasues a particular point of view is presented, it represents all CASA FOI's. The only concensus here would be they all don't agree.
Second, most training providers that do M/E training that I have worked for use the mixture as it is kinder to the engines (loading as already stated). This becomes even more important when you introduce turbos and geared engines.
hope this helps.