Can a company legaly lay off workers before they complete their probationary period, while hiring new ones? (Seemingly to avoid paying benefits)

According to my step son, he is about to be laid off one day before completing his 3 month probationary period at an Amazon warehouse in Quebec Canada. He says even during his final week, they are still hiring new people. He was told by his supervisor that none of the new hires are staying on past their three month period but they encouraged to reapply to the job once let go. Is this common practice or legal?