According to https://github.com/ethereum/EIPs/blob/master/EIPS/eip-712.md#definition- of-domainseparator “Protocol designers only need to include the fields that make sense for their signing domain.”
According to https://github.com/ethereum/EIPs/blob/master/EIPS/eip-712.md#definition- of-domainseparator “Protocol designers only need to include the fields that make sense for their signing domain.”