[makeitdouble]

It depends on the base contract.

I’ve had both cases, with one company coming up with contract “additions” every now and then with super specific terms, including monetary amounts etc. The other companies usually had one single broad contract mentioning that any other provisions would be explicited in the company’s general HR policies. The HR policies get regularily revised, and employees didn’t need to sign every single change.

IMO it probably comes down to transparency. The company going the super granular route had many specific clauses negociated at an individual level, and stuff they wouldn’t want to have in a semi-public document any other employees could look at.