This is the most plausible rationale for doing it with blockchains (see also: many other blockchains)
The whole system appears to rely on a trusted group certifying the [probable] authenticity of an individual's records and Rohingya refugee status, in which case you might as well let them host it on a well-backed up regular database...
It's possible, even easy, to insert fake attestations that biometric B corresponds to identity I. But an append-only log has the advantage over other databases that a simple older-record-wins heuristic is likely to prefer genuine identity records.
A regular database has no way to make it infeasible to insert fake old records. Sure, you can publish checkpoints. But that doesn't work so well when you're up against a government that wants to erase your entire ethnicity.
Isn't the sufficiently determined government with the ability to compromise an organization's computers almost as much of a threat to carry out 51% attacks on its private blockchain as to successfully target distributed copies of database checkpoints?
(In practice, I think the Myanmar government's strategy would simply be to disregard the database rather than to attack it anyway, on the basis the local prejudice against the Rohingya isn't based around their numbers or individual identities but the claim that they are actually Bangladeshi illegal immigrants lying about Myanmar ancestry and land)
Yes, it is a threat. That's why I'm not sure why they're not just using Ethereum. Well, I think I know why -- "let's use Ethereum!" isn't a fundable startup idea. But it's too bad, because I have a feeling Myanmar doesn't have even enough compute power to double-spend a single CryptoKitty.
And yeah, a government would certainly try to ignore facts it didn't like.
The whole system appears to rely on a trusted group certifying the [probable] authenticity of an individual's records and Rohingya refugee status, in which case you might as well let them host it on a well-backed up regular database...