Not entirely correct. Some first hand info:

The rule for max 2 years on temp contracts is only valid for consecutive contracts without interruption. As soon as there's a gap of xx month between two contracts (like in winter), the 2y counter is reset. So they can give you an indefinite amount of temp contracts. This is what is happening now. The same applies if they give you a contract with a function description other than FO (eg if you have a ground function in winter), the counter resets...