Deloitte auditing job offer - no certificate

Hello. My brother got an offer for a senior auditor role at Deloitte France, starting this Monday. He's been working in auditing for a few years, at Deloitte in another country, but just received his college certificate this year due to health issues. He officially got his certificate last month, but hasn't received a copy due to covid processing times. He's supposed to start working on Monday but doesn't have a certificate to show them during onboarding. From your perspective, how much of a problem is this? He's worried they'll rescind the offer, and that they haven't noticed he just graduated this year. I wonder how much is seeing the certificate just a bureaucratic formality versus a dealbreaker? (Granted, I work in tech in San Francisco so I'm from a very different working culture). Could they realistically rescind the offer?