This is a stubborn device, it clings to O750 identity no matter what we throw at it. There's no obvious reason why the O7x0 logo data would display the splash screen yet the correct O6xx data doesn't. It's confirmed as fw_all data for O6x0 in region 14 and it is clearly reacting to the O6x0 ramloader albeit the modified one. Maybe it's time to attempt erasing the nonvol memory, that's a last resort tactic which might work. However, first some questions need answers:
1. Did HWID folder 1651 or 2512 work for the last flash?
2. "After reboot it is still defined as O750" ... On device screen or in Updater.exe or both?
3. Did it display as 6x0 at all this time?