I actually know. And many people know as well. What
@lunar explained is exactly how it is. Almost every time I use my card or before planning a bigger purchase I check those two sites depending on Visa or Mastercard. The rate shown by their calculator is
exactly what my banks show on my statement. At least for USA banks.
It has been that way since Dec-23 when the government changed the credit cards to XE at a rate approximately a bit less than the MEP rate. Those two credit cards only change the rate once per day.