Given the limited range of motion, i think a neck/head single sculpt would have worked fine while still retaining the shoulder shape they have now. To keep the shoulders, the neck would be limited, but it's not super posable now anyway.
Not only would the jawline be more accurrate, but I would think they'd get the musculature a bit more defined and Arnie specific. One thing I hate on figures where the necks aren't attached to the heads is how the necks look like cylinders and don't show any of the anatomy, people's necks don't look like tubes coming out of their shoulders. I get why they do it, you couldn't turn the heads with the musculature in the way.