I suspect, if there are lots of relatively simple ML problems, then a generalist with integration chops will be more effective in getting them out quickly and "good enough". The specialist may take too long on models that are too heavy and impractical.
If there's one big ML problem (Google search, Netflix recommender, Amazon search, etc), where 1% additional makes a difference, then yes, specialist DS/modeler is probably preferred.
Larger, older org/heavier existing infra/more specialized culture will also tilt the scale towards specialists.