Interval brake fluid change

Hello, when buying my used Seat Arona TDI EZ 06/2019, inspection, oil change and TÜV would be made new. Inspection and oil change were due at the time quite normal. From my Skoda I know, that also the brake fluid is changed for the first time after 3 years and then every 2 years. At Seat is also so in the service table. But the dealer meant it only the water content is determined and then decided whether it has to be changed. Is that so new or wants the Hän so only save costs? Sunny greetings from Regensburg