The bolognese we have had in the UK, where we first tasted it, does not seem to have the added cream that we find in the US.
Checked my James Peterson 'Sauce', and 'The Sauce Bible' by David Paul Larousse and they both call for cream.
But I have an Australian book of sauces, and it definitely does not.
OK, OK, I own too many cookbooks.
I think it softens the acidity of the sauce a bit.
But to each his own, and it is good both ways.