I can understand EEPROM vs. FLASH.
FLASH actually is an offspring from EEPROM but you, Joe, knew that already.
Odd as time passes they go to something slower but within good reason for larger storage capacity purposes.
EEPROM was designed to be read a lot more as apposed to written to.
EEPROM uses faster NOR (Not and OR), FLASH uses the slower NAND (Not and AND) type.
NOR type is faster but there is the affordability and storage capacity pro's with FLASH.
10-4, old school here. Remember the days we used to program during ICT, in order to keep up with manufacturing beat, flavor variances)
... it was the concept of being locked while written to, that I didn't see possible.
~ had to google a bit to get reacquainted.