What you say is true: investing in employees attracts top talent. However, that's only one side of the equation. The other side of the equation is that such policies cost money. So in order to say that this policy is a "benefit to shareholders", you'd need to demonstrate that the benefits outweigh the cost, which is of course impossible to quantify. Over the last 5 years, stock in Mercedes Benz Group is down almost 25%, so I wouldn't say that, generally, Mercedes has been good to shareholders.
Is that the best way to evaluate it? It looks like they also offered about $3-4 dividend each year. The stock is down $5 over the last 5 years, but has also produced almost $15 worth of dividends[0].
For comparison, Ford might be up by about 25% (+$2-3) last 5 years, but it has only yielded a dividend of around $3.
