I agree that in the long term, it pays to “get it right first time”, i.e. be able to use composites from the start. However, time and money being limited and risk management (technical) going with fewer or no composites, and then learn and improve gradually is not a bad strategy.
I also can see why they would what to substitute high stress areas with composites first. These high stress areas will have larger therefore heavier structural members. By replacing a few of these you save a lot of weight and some maintenance costs as these member tend to need more hours during maintenance and replacement. Composites will mean they are lighter and require less replacement intervals.