Yes you very very right there as i have found also same as you as some will boot and some won't so i can only guess it is the level of "blocking", imei flagging can have different effects on even same model devices, weird isnt it.
I could go a lot deeper into this because of the work i used to do but i don't think this is the place for that, suffice to say emei is the key and once you turn that around you get results .

But as you rightly said it is most likely only a re-flash it needs hopefully.

I am waiting for the end result from the op and hope it is good news.

Anyhow thanyou for your comments as i do also read many of your very intellectual posts hehehe and enjoy too.