I don't see the risk. It seems German companies are making weak offers with "probation periods" even for international hires. One problem might be that such offers are not very attractive.
The alternative is giving real contracts to international hires, who already have a proven track record (otherwise why would you hire internationally).
Trial contracts were meant for people straight out of college, but in a race to the bottom some companies have started pushing that line further and further, even having people move across the world for temp contracts. You can't complain about labor shortage while behaving like that.
The probation period also applies to you, the employee, if you choose that a company is not for you. Once that period is over, a three month notice period is quite common, so both you and the employer are locked into a relationship.
The probation period balances out how stable employment is once you both agreed that you're a match.