Which Arduino/MCU? Do you see something about checksum? It is open source, you can peek into the code.
If you have in mind ATmega which has real EEPROM, the update() method just compare a byte and overwrites it if it is different. Nothing more. Writing into EEPROM is different as writing into RAM. On C level it uses eeprom_write_byte(), resp. eeprom_update_byte() etc. On system level the EEPROM has separate address space and registers.
For Arduinos, you write your own. There is an example how to calculate the crc. I calculate the crc over the eeprom minus the last 4 bytes and store the 4-byte crc in the last 4 bytes.
If I'm not mistaken, a posted an example. Search for my user name plus eeprom and you should be able to find it. Include crc if needed.