> freely translated: "He always wanted to learn and completed his work to our satisfaction" is basically an F.
Technically even that would be invalid in Austria, if you actually go to the AK (Arbeiterkammer)[1]. So this in turn results in everything being in the superlative. Along with that, the AK is something you just do NOT want to get into trouble with.
In Germany you can also go to court and certain phrasing needs to be dropped according to the courts.
The valuable piece of information in an Arbeitszeugnis that it will tell you is, if the person "verlässt die Firma auf eigenen Wunsch", i.e. if the person resigned from their position, or whether they were let go.
it must not contain negative wording would be more fitting. I find that a bit silly to be honest. On the other hand an employee wouldn't show a bad reference, but it is quite ridiculous.
freely translated: "He always wanted to learn and completed his work to our satisfaction" is basically an F.
Your new employer is allowed to call your old one if the employee consents. He is only allowed to ask about certain things like the content of the reference he gave.