This happens in Germany but it just means that if someone has a simple neutral letter of reference, the person herself is a terrible worker.

You are making the scale from 0 to 10 into another scale of 5 to ten. Employers are not stupid and in fact they have developed their own codes to express whatever they want to express to other employers they have good relationships with.

The same happens in China where it is offensive to say: NO! So , instead of telling it, they wait and tell you Yes(!!)

There is an indirect code to translate the time and emphasis employed by the a yes into a no everybody agrees with.