If the foreign donor gives 50K twice in separate tax years, then the donee doesn't have to report to IRS, right?

The receiver of gift does not pay any tax. A foreign donor is not subject to U.S. taxes.
You may need to file form 3520. Notice of Large Gifts Received from Foreign Persons if the amount is exceeds a limit. The form is due on the date of your return including extensions.The form is filed at Internal Revenue Service, P.O. Box 409101, Ogden, UT 84409

The limit MukatA refers to is $100K, so separate $50K gifts will not have to be reported to the IRS.

However, if there is a clear connection between these separate events and together they are above the limit, you would need to report it.