"Why would you say they are stretching the limits of the law? My understanding is that they had no obligation to renew those 3-month contracts."

Because these 3-month contracts were renewed for years, and in fact, there are many employees who were employed for over 3 years, continuously, by the company. That makes the non-renewal -> layoff.

    "Even if that's the case (highly probable), it would still be a huge improvement compared to the pre-efood era when lots of delivery riders would not be paid on time, work (illegally) with no insurance/pension, sometimes even get humiliated by terrible bosses."

Food delivery platforms are not in the business of providing cash and benefits to drivers. They are in the business of making money. But apparently, they cannot do either.

That's why these labour protection laws exists, to remind those companies even if they think they are not responsible of providing benefits to the drivers that they actually are.

A 3-months contract is not better than non contract at all in the sense that is way tooo short to be able to stabilize your work around it. 3 months contract basically means you'll be as bad as before except that the employer doesn't need to go the illegal route to use the worker (and the employment statistics are better).

Based on what I've read it is more or less the same model we have in my country. Employment contracts are either fixed or indefinite term contracts, you can't renew fixed term contracts indefinitely and they are used in specific situations, one of them being to assess or test someone's abilities before offering an indefinite term contract, so 3 months is a short term but not really in the sense that your new employee doesn't necessarily needs to master the job in 3 months, you just need believe or see that they are learning and being as good as other hires in that amount of time.