When user is creating an expense for a vendor with a foreign currency in the Expense Entries screen, the calculations are correct. However, when user enters the same information into a vendor bill, the Vendor Bills screen uses USD for the vendor instead of the foreign currency.
This is by design. Whether you are creating expenses through the Expense Entries screen or the Vendor Bills screen, the charge amount is in USD. When you enter a cost rate in the Expense Entries screen, it is set to the foreign currency accordingly.