No, factory reset means to open Apps > Settings > Backup and reset > Factory data reset, it can do every fool very fast on street.
But flashing the rom with the manufacturers software means:

  1. You must know how to flash Android phones
  2. You must download new ROM image and know which ROM image you need (It isnt easy if you dont know anything about the phone, only you can see it)
  3. You must have computer with flashing software and special driver for flashing.

It isnt same.