Screening (flash microcontroller and OTP microcontroller)

According to user's manuals, OTP microcontrollers were required to do manual screening after writing user's program in it, but in the case of flash microcontrollers, no mention is made of screening like that. Should I do the screening?

In the case of flash microcontrollers, screening after writing your program in the flash microcontroller is not required.

Why is screening required for OTP microcontrollers and not for flash microcontrollers?

In the case of OTP microcontrollers, until before the assembly process, any data that is written can be erased, so that testing of the PROM part can be done. However, once assembly is done, the contents of the PROM can no longer be erased, so that past the assembly process, PROM write tests cannot be performed. Therefore, the screening after a customer wrote progrem is needed to eliminate PROM defects caused during the assembly process.
On the other hand, in the case of flash microcontrollers, erasure by writing to the flash memory part is possible even past the assembly process. In other words, defects caused during the assembly process are already eliminated in the manufacturing process. Therefore, screening after the customer wrote the program is not required.