[kmitz]

Thanks for the explanation. We bought the laptops from Dell, and after reading your message this is what I found on their website :

"All computers that Dell currently ships are Modern Standby compliant and the above applies. A registry key that Dell leaves in a neutral state controls this behavior, neither prohibiting nor enforcing encryption. Windows interprets this as approval to encrypt." https://www.dell.com/support/kbdoc/fr-fr/000124361/bitlocker...

So for the end-user bitlocker is enabled by default. It is obscure enough that our team missed that they had to backup something before using their computers.